Category: Physics Notes PPT

Can you imagine some gravitational pull of the Sun and the Moon can affect the natural world here on Earth? This phenomenon is known as a tide that occurs in the ocean. In oceans, the rise and fall of the water is a regular and common phenomenon. When these tides occur, the waves move towards the shores and affect the coastlines as well as the maritime activities of the nations. These tides are of various types. In this article, we will be talking about some of its types, such as spring and neap tides, the definition of spring tide or neap tide definition, perigean tide and all the related concepts. This topic will help you in Geography and Geology or Earth Sciences whenever you read about Oceanography.

 

Tides are the waves that occur through the regular change in the sea level caused by the moon and the sun. Tides emerge in the sea and go towards the coastlines. At the time of high tide, the sea is closer to the land, and at the low tide, it is farther away from, and more of the beach can be seen. It is caused by the gravitational pull of the moon and the sun. It happens twice every day. Due to the change of the tides, large quantities of water move towards or away from shore, causing tidal currents. 

 

Spring Tide

Spring tide is one of the types of it. A tide that comes just after a new or full moon when there is a huge difference between high and low water. This is popularly known as a “King Tide” which refers to the “springing forth” of the tide during a new and full moon. It usually occurs three and four times in the year. This tide occurs at a couple of inches to normal spring tides. The term spring is derived from the concept of the tide “Springing forth”. It occurs in the lunar month. 

 

Spring Tide Definition

Some of the standard and recognised definitions are mentioned below:

• “Either of the two tides that occur at or just after the new moon and full moon when the tide-generating force of the sun acts in the same direction as that of the moon, reinforcing it and causing the greatest rise and fall in tidal level. The highest spring tides (equinoctial springs) occur at the equinoxes.” Or “A spring tide is an unusually high tide that happens at the time of a new moon or a full moon.” – Collins dictionary.

• “It is a tide of the greater-than-average range around the times of new moon and full moon.” – Merriam-Webster.

 

Causes of Spring Tides

The various reasons why spring tides occur are mentioned below:

• The forces that contribute to tides are called tidal constituents.

• The moon’s gravitational pull on the earth is the major tidal constituent.

• The greater gravitational force between the objects is close to each other.

• The sun and moon both exert gravitational force on the earth.

• The moon’s pull is stronger than the sun.

• Because it is much closer to the earth than the sun.

• It exerts a tidal force on the whole earth.

 

 

Effects of Spring Tide

The most prominent effect of spring tide is on the tides that take place in the oceans or seas. As we have studied earlier, Spring tides occur when there is a full moon or new moon. During these events, the gravitational pull experienced by the Earth is very high because it experiences the pull from both the sun as well as from the moon. This results in the occurrence of high tides in the seas or the oceans. 

 

Neap Tide

After the seven days of spring tide, the moon and sun are at right angles to each other. These are known as neap tides. It refers to a period of moderate tides. It has small tides. The meaning of it is that the high tides are a little lower, and the low tides are a little higher than average. It occurs because the sun and moon pull the water in different directions.

 

Neap Tide Definition

Some of the recognised and standard definitions are mentioned below:

• “It is a tide of minimum range occurring at first and the third quarters of the moon.” – Merriam-Webster.

• “either of the two tides that occur at the first or last quarter of the moon when the tide-generating forces of the sun and moon oppose each other and produce the smallest rise and fall in tidal level” – Collins dictionary.

 

Causes of Neap Tides

The various reasons why neap tides occur are mentioned below:

• When the gravitational pull of the sun is added to the gravitational pull of the moon on earth, it causes the oceans to bulge a bit more.

• It occurs during the first and third quarter of the moon when the moon appears “half full.”

• During the time of full and the new moon, which occurs when the Earth, sun, and moon are nearly in alignment, the range of the tides is slightly larger.

• This occurs twice each month.

 

Spring Tide and Neap Tide

The spring tides have higher high tides and lower low tides, whereas neap tides have lower high tides and higher low tides. The difference in the range of the water level between high and low tide is much larger in a spring tide than in a low tide.

 

Perigean Spring Tide

A Perigean tide occurs when the moon is new or full and is either closest to the Earth. The full moon or new moon closely coincides with the perigee of the moon. It often occurs six to eight times a year. These are called Perigean Spring Tides. During the time of perigean spring tide, high tides can be significantly higher than the other times of the year.

 

Causes of Perigean Spring Tide

The various causes of the occurrence of perigean spring tide are given below:

• When the Perigean Spring Tide combines with the seasonal changes in the tide, the sea level may cause little coastal flooding in some low lying areas.

• It is referred to as high tide flooding and nuisance flooding.

• Main coastal flooding occurs in response to strong onshore winds barometric pressure changes from a coastal storm.

• Flooding could be worse if a storm strikes during the perigean spring tide.

• Sometimes Perigean Spring Tides have coincided with offshore ocean patterns and l
  arge winds that have resulted in highly coastal flooding.

 

Effect of the Perigee

After 28 days, the moon reaches “perigee.” It is the closest point of the approach to the Earth. This is the time when the gravitational force of the moon is strong. There will be an increase in the average range of tides during these periods. After about 14 days, the moon reaches ‘apogee’. This is the point where the gravitational force of the moon is weak. At this time of the period, the range of the tides decreases.

 

Fun Facts About Tides

• Tides get affected by local conditions prevailing in the region

• At many places, tidal energy is harnessed to run turbines, thereby generating energy and electricity

• Tidal forces also affect solid earth, which in turn influences tides to change shape by a few inches

• The first scientist to claim that tides were caused by the moon was Astronomer Seleucus of Seleucia in 150 B.C.

• Tidal power is the most predictable among all other energy sources

• The varying shape of the ocean floor results in larger tidal energies at some places as compared to other regions

Conclusion

To conclude, we can say that tides are very long-period waves that move through the oceans in response to the force exerted by the moon and the sun if we talk about the types of tides. They mainly are spring tides and neap tides. “Spring tides” are those tides that occurred at that time when the sun and moon both aligned with the earth. And after the seven days of spring tide, the moon and sun are at right angles to each other. At this time, moderate types of tides are produced. 

 

These tides are known as “neap tides.” Spring tides have higher high tides and lower low tides, and on the other hand, the neap tides have higher low tides and lower high tides. There is one more tide which is the type of spring tide, which is called “Perigean Spring Tide”. It only occurs when the moon is new or full and either closest to the Earth. High tides can be significantly higher than the other times of the year. It is also known as the “king tide”.

 

We have learned about tide, spring or neap tide, neap tide definition, spring tide definition and causes, and other related aspects. 

The word “stone weight” is taken from the use of stones for weights, a practice that dates back into the stone measurement. 

So, What is The Definition of Weight?

Weight is the relative mass of the body. It is also known as the amount of matter a body contains. Weight is also called the force of gravity, which acts in the downward direction. 

When the lift moves upward, its product of mass and acceleration goes upward; however, the weight acts downward. 

In this article, we will understand the smallest unit of weight, a stone definition in detail.

Stone Definition

A stone or stone unit of weight, the stone symbol is st. It is an English and imperial unit of mass that is equal to 14 pounds or approximately 6.35 kg. The stone continues in traditional use in the United Kingdom and Ireland for measuring body weight.

What is A Stone?

A concretion of the earthy or mineral, where such a concretion of indeterminate size or shape.

Even in today’s time, we see many fruits and vegetables vendors use stone measurement as a mode of weighing fruits and vegetables.

Significance of Stones

The best way we can discuss the meaning of stones is by referring to their stability or permanence. Irrespective of the purpose of the rock, each stone has a specific purpose and a history that stretches beyond the time limit. Some of them reside outside the universe and some have been home for millions of years. 

The energy these stones bear has something to do with inner energy. This is the reason many cultures use their family stone symbol to meditate or pray. Also, some have faith that stones have spiritual powers. 

The significance of stone symbols revolves around the idea of stability, tenacity, and permanence and the like to define its meaning. 

Furthermore, you’ll find that most of the Stones that are drawn below are talking about having a powerful connection to the meaning of Earth. Besides, they’re generally stable, and they are kinda quite accessible as well. When you connect to the meaning of the stones, you feel the rush of the Earth’s energy inside you. This way, you can get unique and specific lessons that will guide you via life.

Below is the stone symbol that you see in fruits and vegetable shops:

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So, do you know what unit weight is?

If we go with the order of weight, the smallest unit of weight is an ounce, then greater is pound and ton is the largest unit of weight. Stone weight is 6.35 kg, which we call 1 stone in kg.

History of Stone

1. A stone has been traditionally used for weight measurement in the United Kingdom & Ireland.

2. Other countries like England and other Germanic-speaking countries of northern Europe formerly used numerous standardized “stones” for trading purposes, with their values ranging from 5 to 40 local pounds (approximately 3 to 15 kg) depending on the geographic location and objects weighed. However, With the arrival of metrication in the mid-19th century, Europe’s various “stones” were replaced by or adapted to the kilogram.

3. During ancient times, a Biblical law was against the carrying of “diverse weights, a large and a small. The law carried a statement that “no one shall carry a stone and a stone, neither a large nor a small”. 

4. In the Jewish world, there was no standardized “stone”; however, in Roman times, stone weights were created to multiples of the Roman pound. Such weights constantly changed in quality, like, the Yale Medical Library held between 10 to50-pounds and these were stated examples of polished serpentine, while a 40-pound was an example at the Eschborn Museum made of sandstone.

Stone Unit of Weight

Below is the chart that shows the value of a stone unit of weight with various units:

Metric Stone

In the city of the Netherlands, the metric system was adopted in 1817, the pond a.k.a pound was set equivalent to a kilogram, and the steen a.k.a stone was previously been 8 Amsterdam pond, i.e., 3.953 kg, and was redefined as 3 kg.

Ordinarily, during the modern period in Dutch, a pound was used as an alternative to 500 grams/half a kg, while the ounces was used for a weight of 100 gms, being equal to 0.2 pounds.

Temperature is a physical property to tell you about the coldness and hotness of a body. Celsius, Kelvin or Fahrenheit are the scales to use for recording temperature, and these scales have a correlation to convert one reading into another scale reading.

In the notes, has provided a detailed explanation about temperature, thermometers and examples of temperature measurement. Also, physics experts at have offered you the relation between temperature and kinetic energy. Students can learn more about the topic from online class for physics, where you study each concept with the help of 3-D illustrations and examples.

Notes on Temperature

gives you correct and helpful content to boost your knowledge, also ease the process to retain the concepts for a long duration. Various subject matter experts for physics have made these resources to provide you with in-depth knowledge to gain good marks in the examination. 

Experts of physics at have made sure to provide you with easy notes on temperature, including the use of thermometers, units of temperature and absolute zero. Students also get to learn about the difference between hotness and temperature.

Temperature Scales with

There are three temperature scales to study in this chapter; each scale is different and has different upper and lower fixed points, and widely preferred temperature scales are Celsius and Fahrenheit. notes give you exposure to the new and exciting examples that help you understand the significance of each scale in measuring temperature. 

has explained the relationship between these scales to convert one reading into another scale. For example, in India, we use a Celsius scale that has  0 ^oC as the lower fixed point, which is the freezing point of water, and 100 ^oC as the upper fixed point, which is the boiling point of water. All the basic details are necessary to learn about different thermometers, and experts have made sure to add them into the notes. Also, you can join online tuition classes for physics to study these thermometers or scales with the help of expert teachers.

Register at to Learn Smartly

Register to pro classes to start studying under the guidance of the subject matter experts of various subjects. They not only just teach you about the applications of a particular concept but also provide one-on-one support to clear all your doubts. 

Sign up to classes with your valid email id and enjoy learning smartly. 

More About Temperature

In Physics, temperature refers to the physical properties of matter, which quantitatively expresses the hotness or coldness of a body. Before the evolution of the concept of temperature, we used to judge temperature on the basis of human perception – whether an object is hot or cold was mostly judged by human touch. However, this is not accurate. For example, during a cold morning, a wooden table might seem warmer than a metal cycle rod. However, both have an equal temperature based on the external atmosphere. Metal, being a better conductor of heat, draws heat out of your body faster, making it cooler than the wood (a poor conductor of heat). A simple temperature definition in science is the physical quantity measured using a thermometer. However, the temperature is related closely to the kinetic energies of the molecules and atoms inside an object.

Temperature and Kinetic Energy

The kinetic energy of an object, as per physics, is the energy that an object possesses due to its motion. Every molecule or atom has kinetic energy. Even in solids, when the molecules are tightly packed, all of them contain vibrational energy. Temperature is referred to as the average kinetic energy of all molecules. When a substance absorbs heat, the molecules start to move faster. This increases its kinetic energy. As a result, the temperature of the substance starts to increase. Eventually, the movement of molecules can result in the separation of the molecules as they start moving farther away from one another. For example, in solids, when the temperature increases, the molecules start moving faster, and this leads to the expansion of the solid. Eventually, if the temperature rises to the melting point of the solid, it can change its state as well. The sum of all kinetic energy in a body is called heat. Heat is a form of energy, and it can get transferred from one body to another.

Example of Temperature 

Many people often think of temperature as energy, which is not true. Temperature is just a measurement that shows the average kinetic energy of one atom or molecule. Hence, when we say something is hot or cold, we are generally using another reference point to define the hotness and coldness of a body. For example, if we say that the coffee is hotter than the ice-cream, we are using the ice-cream as a reference point to determine the temperature of the coffee. During weather reports, temperature and humidity are shown in two different columns. This is because hot and humid days are considered hotter than hot and dry days because of human perception rather than temperature changes. If the temperature of a day is the same, but the humidity is high, then a person might feel hotter since humid days do not evaporate sweat as fast as dry days do. Evaporation of sweat helps us stay cooler. 

What is the Absolute Zero?

Absolute zero is the lowest possible temperature. It has been marked at 0 Kelvin or -273.15 degrees Celsius or -460 degrees Fahrenheit. At absolute zero temperature, there is no heat energy present in a substance. At this temperature, the particles present in a perfect crystal will remain motionless, that is all kinetic energy in the particle will become zero. Absolute zero is theoretically possible, but practically, we have not reached absolute zero temperatures yet. However, we have been able to reach close to absolute zero by using cryocoolers and dilution refrigerators.

Units of Temperature

Since temperature is a physical quantity, it has units that represent it. The SI unit of temperature is Kelvin. However, we also use two other units to measure temperature – Celsius, and Fahrenheit. The units of temperature are related in this manner:

oC = 5/9 (oF – 32)

K = oC + 273

How do Thermometers Measure Temperature? 

Thermometers are generally used to measure the temperature of a body. A thermometer has two important components – a temperature sensor like the bulb of a mercury-in-glass thermometer and a numerical scale. The mercury thermometer works on the principle of thermal expansion. Thermal expansion is the change in the volume of a substance due to the change in temperature. Since mercury is sensitive to temperature changes, it is used in thermometers. An increase in the temperature is quickly registered as the mercury inside the thermometer expands and rises upwards. The numeric scale in the thermometer gives the measurement of the temperature. There are three kinds of thermometers – Celsius Thermometers, Fahrenheit thermometers, and Kelvin Thermometers.

Temperature Scales

Since thermometers have to be of a specific length, each thermometer has a fixed scale. Celsius thermometers are easy to manufacture as the fixed scale used for them is set at the freezing point and boiling point of water. Celsius thermometers have a lower fixed
point set at 0 oC (freezing point of water) and 100 oC (boiling point of water). Fahrenheit thermometers have a lower fixed point at 32 oF and an upper fixed point at 212 oF. Kelvin thermometers have a lower fixed point at 273 oK and an upper fixed point at 373 oK. From these fixed points, we can derive the relationship between Celsius, Fahrenheit, and Kelvin too

[frac{C}{100}] = [frac{F-32}{180}] = [frac{K-273}{100}]

When we talk about thermal energy, we refer to the heat energy that is produced when there is a rise in temperature. This rise in temperature causes the atoms and molecules in a material to vibrate at a high frequency. It will eventually collide with each other. As a result, energy is dissipated from them, which is called thermal energy. Now that we know what is thermal energy let’s take a look at the thermal energy definition.

Thermal energy is defined as when any atoms or molecules of an element start vibrating due to the rise in temperature; it produces energy which is called thermal energy. In other words, thermal energy definition can be the movement of atoms and molecules. These atoms and molecules will keep moving faster as the temperature rises. Therefore, we can say that the kinetic energy of the particles and their thermal energy is the same. Now that you are familiar with what is thermal energy and the thermal energy definition, we will see the different sources of thermal energy.

Sources of Thermal Energy

• Chemical energy: We can convert chemical energy to thermal energy. Some good thermal energy examples are the burning of wood and coal.

• Solar energy: Solar energy comes under the best sources of thermal energy. It is the cleanest and readily available source of energy.

• Mechanical energy: We can convert mechanical energy to thermal energy. An excellent thermal energy example is the energy released due to friction.

• Fossil fuels: Fossil fuels are burnt to produce thermal energy.

• Geothermal energy: We can convert geothermal energy to thermal energy. A good thermal energy example is the energy released due to volcanoes, hot springs, and geysers.

Thermal Energy Storage

It is crucial to understand exactly what is thermal energy storage. Energy storages are designed to store energy, and when the demand for power increases, it can maintain a constant supply. It helps to keep the supply and demand for energy, use renewable sources of energy, and increase the efficiency of the use of energy. Thermal energy storage is a technology that stores up thermal energy. It is obtained by continuously heating and cooling the storage system. The energy stored can be utilised in the future when the need arises. By using energy storage, we can reduce the time and rate mismatch between the supply and demand for energy.

Take solar energy for an example. Solar energy can only be produced during the day when the temperature of the environment increases. But the same energy is utilised day and night. Therefore, storing energy becomes essential. By storing the thermal energy during the day, we can use it at night.

Working of Thermal Storage Energy

To properly understand the working of the thermal energy storage system, we will look at an example relating to an air-conditioning system.

The image shows the various steps in the working of thermal energy storage.

In the first step, during night time, we take a mixture of water and 25% of propylene glycol or ethylene. This mixture is then cooled with the help of a chiller. In our example, we are using an ice storage cooling system. The next step is to circulate this mixture in the ice bank, which acts as a heat exchanger. In the tank, we can freeze 95% of the water. Then ice is uniformly created inside the container with the help of the heat exchanger.

Now, during the day time, the glycol from the mixture can freely move between the ice. This glycol is then used to deliver the stored energy into a room of a building. A fan is used to blow off the cold atmosphere into the room.

There are two main types of thermal energy storage. The first type of thermal energy storage is sensible heat storage. In this type, heat energy is stored in either liquid material or solid material. The second type of thermal energy storage is latent heat storage. In this type, heat energy is either stored in Solid-Solid material, Solid-Liquid material, or Liquid-Gas materials.

Different Types of Thermal Energy Storage

Thermal Energy Storage Applications

Thermal energy is a good source of energy. Let’s look at some of the good uses of thermal energy.

• We use thermal energy in solar power plants to provide energy during the night time.

• Thermal energy is used in cooking, baking, water heating, and heating.

• It is also used in thermal processing of non-metals.

• It has applications in automobiles.

• They are used as incinerators to burn down waste.

• It has applications in thermal power plants.

Tides are the rise and fall of sea levels caused by the combined effects of the Moon and Sun’s gravitational forces, as well as the Earth’s rotation.

Tides adjust the depth of the sea and create oscillating currents called tidal streams, making tide prediction crucial for coastal navigation.

The intertidal zone, which is a stretch of seashore that is underwater at high tide and exposed at low tide, is a significant ecological product of ocean tides.

The changing ocean tides created at a given location on the Earth is the product of the Moon’s and Sun’s changing positions relative to the Earth, as well as the effects of the Earth’s rotation and the local bathymetry.

Despite the fact that the Sun’s gravitational force on the Earth is about 200 times greater than the Moon’s, the Moon’s tidal force is about twice as large as the Sun’s. This is because the tidal force is proportional to the gradient of a gravitational field, not to its strength.

Since the Sun is about 400 times farther away from the Earth than the Moon, the gradient of the Sun’s field, and thus the tidal force created by the Sun, decreases more rapidly than the field strength with distance from the source.

Due to a variety of variables that decide the lunitidal interval, tides differ on timescales ranging from hours to years. Tide gauges at fixed stations monitor water level overtime to make reliable records. Variations produced by waves with intervals shorter than minutes are ignored by gauges. These figures are compared to the reference (or datum) level, which is commonly referred to as mean sea level.

While sea tides are the most common cause of short-term sea-level fluctuations, storm surges can also be caused by forces such as wind and barometric pressure changes, particularly in shallow seas and near coasts.

Why Tides Occur?

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• Earth and its water bulge out on the side nearest to the moon and the side farthest from the moon due to the tidal force. High sea tides cause these water bulges.

• Every day, the area of the Earth moves through both of these bulges as the Earth rotates.

• A high tide occurs while you are in one of the bulges.

• A low tide occurs when you are not in one of the bulges.

• On most days, this pattern of two high tides and two low tides happens in most of the world’s coastlines.

• Tides are just all about gravity, and the moon’s gravity is what causes the daily tides.

• The moon’s gravity pulls on various parts of our earth as it rotates.

• Even though the moon is just around 1/100th the mass of Earth, it has enough gravity to shift objects around because it is so close to us. Even the land is pulled by the moon’s gravity, but not enough for us to notice.

• Everyone is bound to notice when the moon’s gravity pulls on the water in the oceans. Water moves far more easily than air, and it likes to bulge in the direction of the moon. This is referred to as the tidal force.

• The water on the moon’s side still tries to bulge out into the moon due to the tidal force. A high tide is what we term this bulge. A high tide can occur as your part of the Earth rotates into this bulge of water.

• The Earth is not coated in an equal layer of water like a global ocean. There are seven continents, and land is a major obstacle. The continents obstruct the water’s ability to pursue the moon’s pull perfectly. As a result, the difference between high and low tide in some areas is minimal, while in others, the difference is significant.

• The moon’s gravitational force is strongest on the side of Earth that faces it directly. On that side, the water is firmly pushed in the direction of the moon.

• The moon’s gravitational force is weakest on the side of Earth closest to the moon. The gravitational force of the moon on the whole planet is roughly averaged at the Earth’s centre.

• We deduct the average gravitational pull on Earth from the gravitational pull at each position on Earth to get the tidal force, which is the force that causes the tides. The Earth is stretched and squashed as a result of the tidal force. The two tidal bulges are caused by this.

• Since the Earth’s surface rotates around each of the bulges once a day, there are two high tides and two low tides in a single day.

• Tides are caused by the Sun in the same way as the moon does, though they are smaller.

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• When the earth, moon, and sun align, as they do at full and new moons, the lunar and solar tides strengthen each other, resulting in more intense tides known as spring tides.

• When the lunar and solar tides oppose each other, the outcome is neap tides, which are unusually small tides.

• Every two weeks, there is a new moon or a full moon, so high spring tides occur frequently.

• The water level is also affected by wind and weather patterns. Strong offshore winds will push water away from coastlines, causing low tides to be exaggerated. Water can be pushed towards the shore by onshore waves, making low tides less visible.

• Sea levels can be pushed down by high-pressure weather systems, resulting in lower tides. Tides that are much higher than expected can be caused by low-pressure systems brought on by powerful storms and hurricanes.

Types of Ocean Tides

In this tide information, we will learn about different types of tides and the regions where they occur.

1. Semi-Diurnal Tides

Every day, a semi-diurnal tidal cycle has two almost identical high tides and two low tides. The time between high and low tides is approximately 12 hours and 25 minutes. The Indian Ocean is home to the most Semi-Diurnal Tides. The Eastern African Coast and the Bay of Bengal are two other common coasts with semi-diurnal tides.

2. Diurnal Tides

There are four tides in a day of diurnal tides. The sun produces two tides, and the moon produces two. Springtide is a particularly high tide brought about by the Sun’s complementary position in relation to the moon. It’s worth noting that the Syzygy occurs when the Sun, Moon, and Earth are all in the same line. There are two forms of syzygy:

When the moon and the sun are on the same side, it is called a conjunction.

When the moon and the sun are on opposite sides, it is called opposition. The magnitude of the tide would be the same in all of these situations.

3. Mixed Tides

The mixed tidal cycle, or simply mixed tide, is formed by a tidal cycle of two unequal high and low tides. There are semi-diurnal and diurnal oscillations in this tidal cycle. It can be found all over the Gulf of Mexico and the Caribbean Sea. Mixed tides can also be found along the Brazilian coast in the southeast.

4. Spring Tides

When the sun and the moon are in alignment, spring tides form, pulling the ocean surface in the same direction. A spring tide occurs as high tides are higher and low tides are lower. It happens twice in a lunar month. The name King Tide has also been given to it.

5. Neap Tides

The spring tide is followed by the neap tide, which happens seven days later. The fact that the sun and the moon are at a right angle to each other is the most noticeable feature. The first and last quarters of the moon are when this tide happens. The moon’s gravitational pull and subsequent oceanic bulge are cancelled out by the sun’s gravitational pull and resulting oceanic bulge. In addition, in comparison to spring tides, neap tides have lower high tides and comparatively higher low tides.

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Characteristics of Tides

• Flood Tide – The sea level can increase for a period of many hours.

• High Tide – This is when the water level reaches its highest point.

• Ebb Tide – This is a point in which the sea level continues to fall for a period of several hours.

• Low Tide – When the seawater level begins receding, it is called a low tide.

Tides in Power Generation

• Tidal energy can be extracted in two ways by incorporating a water turbine into a tidal current or by constructing ponds that release/admit water through a turbine. 

• In the first instance, the sum of energy is completely dictated by the timing and magnitude of the tidal current. However, since the turbines will block the ship’s passage, the best currents could be inaccessible. 

• In the second, impoundment dams are costly to construct, natural water cycles are interrupted, and ship navigation is hampered. With multiple ponds, however, power can be produced at specific times. 

• Aside from environmental concerns, engineering problems include merely surviving corrosion and biological fouling. 

• Proponents of tidal power argue that, unlike wind power, generation levels can be reliably predicted, with the exception of weather effects.

• While some generation is possible for the majority of the tidal cycle, turbines lose efficiency as they operate at lower speeds. 

• The periods that high power generation is possible are limited because the power available from a flow is proportional to the cube of the flow speed.

Importance of Tides

• During ebb tides, fishes will gather in groups. Commercial fishermen learn to fish at peak concentration levels and follow the tides to increase their economic investment and make better use of their time. Ebb tides are also good for recreational fishing since the concentrations of smaller fish attract the larger trophy fish. Tides have an effect on other facets of ocean life, such as fish and ocean plant reproduction. Tidal waves carry floating plants and animals between spawning areas and deeper waters. The tides assist in the removal of toxins and the circulation of nutrients that ocean plants and animals need to live.

• The coastal zone is home to crabs, mussels, snails, seaweed, and other edible marine life. Tiny fish and sea vegetables can be found in small tide pools. Sealife in these areas is often harvested for food. These diverse and plentiful species would perish if the tides were not washed on a regular basis, and food supplies would be depleted.

• The depth and currents in and around coastal areas are affected by tides. In certain places, ships can need to cross the seas during high tide to avoid running aground. When determining the best time to fly, pilots consider the water level, channel width, and water flow direction. To get tall loads under bridges, pilots can choose to fly when the tides are at their lowest. Tidal flows can aid or obstruct a ship’s progress in the water. The current can be used by pilots to get the craft where it wants to go. The efficiency of marine and inland shipping can be improved by having a detailed understanding of how tides influence navigation and how to use tides in navigation.

• The weather is affected by tidal waves and tides, which churn up the ocean waters. Tides and tidal currents combine arctic water, which can’t absorb much light, with warmer topic water, which can. The stirring creates more stable and habitable climate conditions, as well as balancing global temperatures.

• Every 24 hours, there are two high tides and two low tides. The predictability of the tides, as well as the rapid movement of water during the inflow and outflow, will provide a renewable energy source for coastal communities. Hydroelectric plants can use the flow of water in the same way as rivers do.

Conclusion

Understanding the gravitational force of the Sun and Moon will help us understand how tides work. The gravitational force between these bodies is determined by their mass and the distance between them. That the Sun is far further away from the Earth than the Moon. As a result, the Earth’s gravitational force is weaker than the moon’s. As a result, the tide’s magnitude is determined by the moon. It is commonly assumed that the gravitational pull only affects water bodies, but this is not the case. The gravitational pull affects both land and water bodies. The impact of gravitation on water bodies is greater since the relative pull of the ground is less than that of water.

The focal length of a convex lens is the distance between the center of a lens and its focus. The focal length of an optical instrument/object is a measure of how strongly/sharply the system converges/diverges light and it is just the inverse of the optical power of the system. 

The focal length of convex lens formula is object distance multiplied by the image distance divided by the difference of the object distance and the image distance.

Here, we will discuss how to find the focal length of a convex lens, perform the convex lens experiment Class 12 to obtain the focal length of a convex lens.

To find the Focal Length of a Concave Lens using Convex Lens

Now, we will understand the procedure to find the focal length of a concave lens using convex lens:

Aim:

To determine or To find the focal length of a concave lens using convex lens by using the following two methods:

1. A lens in contact method, and 

2. A lens out of contact method.

Theory Part:

A concave lens is thinner at its center than its edges as compared to a convex lens. So, when the white light passes through the concave lens, it spreads in all directions and this is the reason we call the concave lens a diverging lens. 

The nature of the image formation in the concave lens is virtual and diminished. 

Now, we know that the image formation is diminished so it becomes difficult to find its focal length. That’s why we are performing an experiment to find the focal length of a concave lens using a convex lens. Also, there are two methods of finding the focal length of concave lens:

1. A Lens in Contact Method

When a concave lens of focal length fb is placed on the common axis (coaxially) in contact with the convex lens of focal length fa, then the focal length ‘F’ of the combination is:

1/F = 1/fa + 1/fa

Therefore, a formula for focal length of concave lens is:

fa = (F X fa)/ (fa – F) cm

2. A Lens Out of Contact Method

Materials required:

Theory Part

The real image ( i1) formed by the convex lens works as a virtual object for the concave lens. When a concave lens is interposed/affixed between the convex lens and the real image i1, a new real image forms which is ‘i2.’

If ‘u’ is the distance of the concave lens from the real image i1, and v is the distance from the real image i2, then the focal length of the concave lens is:

1/f = 1/v – 1/u (We call this the focal length of convex lens formula)

And,

f = (uv)/(u-v)

This is the formula for focal length of concave lens which states that the focal length is the product of the image distance and the object distance divided by the difference in the object and the image distance.

Convex Lens Experiment Class 12

• Keep the given concave lens of focal length in contact with the convex lens of focal length f. This forms a combination of two thin lenses in contact.

• Make sure that the arrangement of lenses is between the shining wire gauge and the screen at a fixed distance from the gauze, which is ‘u’ cm.

• The screen is adjusted in a manner to obtain a clear image of the wire gauge on it.

• Measure the distance of the combination of lenses in contact from the screen, which is ‘v’ distance.

• Now, to obtain the focal length of the combination lens, we have the following:

 F  = (uv)/(u + v) cm

From this formula, we get the way to find the focal length of a convex lens/find focal length of a convex lens.

• Keep on repeating the above experiment by positioning the combination of thin lenses at various distances from the shining wire gauge. 

• Now, we will calculate the mean value of F, as we have done so many Convex Lens Experiment Class 12.

• By using the value of the focal length of concave lens, fa, and the focal length of the combination, i.e., F,  we can obtain the formula for focal length of concave lens and then find the focal length of concave lens:

fa = (F X fb)/ (fb – F) cm

Now, let’s record our observations for future reference:

Calculations

1. The focal length of the combination lens  ‘F’ is:…….cm.

2. To obtain the focal length of a convex lens fb, we get the values as …..cm.

3. Now, we get the focal length of the given concave lens as;

            fa = (F X fb)/ (fb – F) cm = …….cm.

Why study this Topic?

This topic is an essential experiment that is asked in a practical exam. This experiment in ray optics enables a student to identify how to focus lenses for be
tter image and also informs best practices in the study of lenses. This experiment also enables a student to draw a graphical representation of the observations made.

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