Category: Physics Notes PPT

We, humans, have an instinctive tendency to judge a matter by the laws of cause and effect; it is the only thing that has remained intact during the process of human evolution. This tendency has busied over the happenings of the natural world while we took each step at a time to the concept of science, which we have today. The modern definition of science relies on observation and experimentation through the path of scientific discoveries has been initiated by ancient Greeks and Romans, trying to logically describe various natural phenomena. Ancient science, however, laid the founding stone for the scientists of the later stages to embark upon. It has been claimed by many that Aristotle was the first scientist. He came around the 4th century BC and brought with him the origin of science.

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Historical Development of Science

Science is a practical and intellectual activity that relies upon the systematic study of the structure and behavior of every natural and physical object through the process of observation and experiment. Since the dawn of the origin of science, many aspects of the world have been called into question. Still, it can be sorted in three main categories based on the subject of study- natural sciences, social sciences, and formal sciences. 

1. Natural Sciences – It comprises the study of the material world.

2. Social Sciences – The study of people and societies.

3. Formal Sciences – It is the domain of mathematics. 

Historical Evolution of Science

We have earlier discussed the definition and the origin of science; in this section, we will trace the slow transition of science as we progressed over the eras and the scientific development we have achieved from the ancient science to the modern. A quick fact: the word ‘Scientist’ had not come into being until the 19th century, when William Whewell first coined the term. 

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• Before the writing system came into being, scientific knowledge and findings were transferred in the medium of oral tradition. Ancient science followed this process.

• The scientific revolution has occurred in many stages over the years, and each one has bought myriads of scientific ideas together developed by evolved thinkers. In the early stages, when Churches had the upper hand over the people in Europe, original and logical thoughts were condemned; however, the truth cannot be suppressed. One such instance was the findings of Nicolaus Copernicus, who inferred that Earth was not the center of the universe, and first bought the idea of the solar system in the 16th century. Later, Johannes Kepler developed the model of planetary motion.

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• Another one of those revolutionary thinkers was Galileo Galilei, who came around the 17th century. He is known as the father of Modern Physics. The further strengthened the ideas of Copernicus and Kepler by inventing the telescope and looking beyond the Earth’s atmosphere.  

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• Later came, William Gilbert, who conducted various experiments with magnets and electricity. He proved Earth itself was magnetized.

• As the study furthered, it was categorized into groups. Natural sciences comprise Physics, Chemistry, Geology, Astronomy, and Biology. Social sciences include the study of political science, geography, linguistics, economics, psychology, sociology, anthropology. 

Science Facts

Here we have collected some amazing science facts that you probably learn in high school. These prove that science can be fun and informative at the same time.

1. Water is very prone to do some fun stuff. Water can be boiled and frozen at the same time.

2. 20% of all the oxygen that is present in Earth is produced from the Amazon rainforest.

3. Venus is the only plant that is spinning in a clockwise rotation.

4. The light we receive from the sun has a travel light of 8 minutes and 19 seconds. Light has the fastest velocity that humans have known. Albert Einstein and Issac Newton have conducted many experiments with light.

5. The acids that are present in the human stomach can even dissolve razor blades.

Did You Know?

It has been claimed by many that Aristotle was the first scientist. He came around the 4th century BC and brought with him the origin of science. The speed of light is around 186000 miles per second. Gravity was first discovered by Sir Issac Newton. Though a deduction, it has been conjectured that if one particle travels at the speed of light, there is a possibility that it can travel through time, though it still remains in the genre of science fiction. 

Solved Examples

1. Who is the founder of natural science?

Sir Issac Newton has been claimed as the founder of natural science by many scientists, principally because of his groundbreaking work in The Mathematical Principles.

2. Who is the founder of science?

It has been claimed by many that Aristotle was the first scientist. He came around the 4th century BC and brought with him the origin of science.

The distant galaxies are moving away from the earth. In other words, the universe is expanding. Considering this fact, Georges Lemaitre gave an important physical cosmological result known as Hubble’s Law, which explains the correlation between the distance to a galaxy and the redshift. According to the law, the recessional velocity or the redshift is directly proportional to the distance of the velocity. In layman’s language, the law of Hubble meaning states that the farther the galaxies are from the earth, the faster they recede away from it. The Hubble’s law is not only evidence of the expansion of the universe, but also an important explanation to the big bang model. Below we have given the formula of Hubble’s Law. 

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The Numerical Expression for the Hubble’s Law

v = H0d

v = Recession velocity in km per second

d = Distance in Mpc

H0 = Expansion Rate Today [Hubble Parameter]

In this section, we’ll be deriving a numerical expression of the Hubble’s Law. As we discussed in the previous section, The Hubble effect shows the direct correlation between the earth’s distance to a galaxy and its recessional velocity. Thus, numerically, Hubble’s law can be written as 

[v propto r]

Where v represents the recessional velocity in km/s and r represents the distance of the galaxy in mpc.

For removing the proportionality, we require proportionality constant. This proportionality constant is known as the “Hubble constant” is denoted by H0. Thus, we get the Hubble’s law as

v = H0r

**The Hubble constant (H0) measured in Km/s/Mpc.

The Hubble Constant (H0) 

The Hubble constant is a unit representing the pace of universe expansion concerning a particular point in the universe. While solving problems for the Hubble’s law, we’ll be taking the Hubble constant in Km/s/Mpc.

Till now, there have been a lot of attempts for calculating the exact value of the Hubble constant as the Hubble constant keeps on changing. The current direct measurement of the Hubble constant is taken as 73.8 km/s or 2.4 km/sec/Mpc.

Redshift – Meaning and Definition

Redshift is a phenomenon resulting in an increase in the wavelength of electromagnetic radiation from an object. There are 3 main causes of redshift:

• Doppler Effect: The movement of objects closer or apart in space.

• Hubble Effect: The universe is expanding constantly. This expansion is resulting in the separation of objects without a change in their position. This is referred to as cosmological redshift.  

• Gravitational Redshift: Gravitational redshifts result in distortion of space-time and exertion of force on light and other particles due to strong gravitational fields.

[z = frac{lambda – lambda_{0}}{lambda_{0}}]

z = redshift

[lambda] = measured wavelength shift

[lambda_{0}] = true wavelength

The phenomena of redshift can be expressed numerically in an equation, known as the redshift equation, which is given by:

[z = frac{delta lambda}{lambda}]

Where z denotes the redshift, λ denotes the wavelength, and Δλ denotes the shift in the wavelength in the spectra.

Relativistic Redshift

[z = sqrt{frac{c + v}{c – v}} – 1]

z = redshift

v = recessional velocity

c = speed of light

Relativistic redshift is very useful for dealing with large values while solving problems related to the Hubble effect. Relativistic redshift perfectly substitutes the Doppler formula when the velocities are too large to be represented by the Doppler formula (generally for the velocities greater than 10% of the speed of light).

Let v represent the velocity of the object measured, c represents the speed of light and z represents the redshift, then the relationship can be expressed as

[z = sqrt{frac{c + v}{c – v}} – 1]

Limitations of Hubble’s Law

One can calculate the distance of the galaxy using Hubble’s equation after determining the shift of light into the redshift. Besides being an important result in physics, Hubble’s law still confers some limitations, which are as follows:

Did You Know?

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The renowned Hubble space telescope is also named after Edwin Hubble. The telescope has been providing important information and images for research since 1990 when it was carried to the orbit. An asteroid and moon crater have also been named after Edwin Hubble for his valuable contribution to the fields of astrophysics.

Solved Examples on Hubble’s Effect

1. Galaxy NGC 123 has a velocity away from us of 1,320 km/s and the Hubble Constant’s value is 70 km/s/Mpc. How far away is the galaxy according to Hubble’s Law?

Answer: We are given a numerical based on the Hubble effect. 

According to the question, 

The recessional velocity (v) = 1320 km/s (the velocity at which the galaxy is moving away from the earth)

Hubble constant (H0) = 70 km/s/Mpc

We need to find the distance between the earth and the galaxy i.e. r.

Using Hubble’s law, we get

v = H0r

1320 = 70 r

r = 18.85 Mpc

The word ‘igneous’ has been derived from the Latin word ‘Ignance’ that means hot or fiery. Igneous rock is a Latin word that means hot or molten rock that crystallizes and solidifies in the following shape:

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The Earth’s crust is made up of different types of rocks, the rock that makes up the maximum volume of Earth’s crust is called the Igneous rocks.

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Igneous rocks are found beneath the ocean crust and these are formed entirely of basaltic rocks with peridotite below the mantle. These basalts also erupt above the Earth’s subcontinent zone either in volcanic islands or along the sides of the continents.

What are Igneous Rocks?

In this article, you will learn about the types of igneous rock and their formation.

The rocks are associated with volcanic eruptions. The liquid matter coming out of these volcanoes is called ‘magma’, it is a hot liquid that is made up of molten minerals.

Now, when this magma reaches the Earth’s surface, it is known as ‘lava’. The cooling and solidification of lava at the Earth’s surface results in the formation of Extrusive Igneous Rocks; these rocks are also known as ‘Volcanic Rocks’. Due to rapid cooling, their crystals are fine-grained.

The image below shows the volcanic or extrusive igneous rock:

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However, some of the magma cannot come out and settles inside the surface; this magma cools slowly under the Earth’s surface, as it is surrounded by the soil and rocks present all around it.

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So, the cooling process and solidifying of magma at a depth within the Earth’s crust result in the formation of rocks having large crystals known as Intrusive Igneous Rocks. 

The below image shows the intrusive igneous rock:

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So, we studied the two types of igneous rocks viz: Intrusive igneous rocks and Extrusive igneous rocks with their formation. 

Fun Fact

It is fascinating to note that igneous rocks were the first to be formed and are also known as ‘primary rocks’. 

Igneous Rock Example

Since there are many igneous rocks and it’s really hard to distinguish between these. Now, let’s identify the types of igneous rocks.

How to Identify Igneous Rocks?

So far we understood that igneous rocks are those formed by the cooling and solidification of magma or molten rock. As the melted rock cools, new minerals and textures are formed on the basis of things like the original magma composition and the addition of any new chemical components surrounding rocks. 

The time it takes for cooling and the temperature and the pressure at which it cools depends on various factors. Since there are so many variations in this process of formation of igneous rocks because of varying textures and compositions, so it becomes paramount to study their types to classify each one of these.

When we identify or classify igneous rocks, we look for textural and compositional clues in the rock that describes the story of magma formation and its cooling process. It’s because the magma formation and cooling process and the link between these two help us determine the formation environment of igneous rocks with its history. Now. let’s get started. 

Igneous Rocks: Textures and Composition

The below table describes each igneous rock according to its respective texture and composition

If we look at the above table, the five columns represent the five basic textures and the four rows represent the four basic compositions. Through this table, we can classify something about igneous rock formation and their history.

Magnum that solidifies and cool so slowly underneath often take hundreds to thousands of years or quickly above the ground following an eruption.

Igneous Rocks and its Types

Magna never reaches underground instead they reach the magnum chamber or insert themselves into cracks or between layers in the rock over a long period of time. They cool and the atoms in the molten state bind with each other to form minerals that are most stable based on their existing temperature, pressure, and chemistry. 

The slow cooling process allows for large crystals formation; the texture of these rocks is described as Phanretic and these crystals are large enough to be visible through the naked eye. The subcategory of Phanretic rocks are usually large crystals and are called Peg Mafic rocks; the rock displaying this texture is called Pegmatite.

In any case, large crystals are formed when magma cools slowly and the magma viscosity is very low then the water is added to it. Due to the low viscosity, the atoms flow quickly that small inches of crystals are formed because when magma erupts as lava, atoms don’t get enough time to form large crystals. Such is the case of extrusive igneous rocks.

The gravitational interaction between celestial bodies in our solar system gives rise to the well-known tidal waves at the planets. The tidal waves that originate at the Earth’s crust perpetually transform the microstructure of the Earth’s crust leading to a variation of the concentration of natural radioactive gases in the terrestrial air and to varied conditions of their leakage to the Earth’s atmosphere. 

These variations give rise to bursts of thermal and slow neutrons in the vicinity of the Earth’s crust because the radioactive gases are the sources of energetic alpha particles that induce neutron production upon the interaction with the nuclei of elements of the Earth’s crust and the atmosphere. In this process, the idea of the production of the neutron in the ground coat is extended to the other celestial bodies interacting with one another. 

Celestial Bodies

The celestial bodies or the celestial objects are the elements that are located outside the earth’s atmosphere. The celestial bodies will be far away from the earth and the distance measured will be in light-years. The best example for the celestial bodies is the moon, mars, all the planets, stars, etc., all together form the universe. The glorious starry night sky is filled with such objects and when we observe them with a telescope, they reveal fascinating aspect and beauty of the worlds of their own. Since all the celestial bodies are so far away, we cannot observe all of them using the naked eye and hence we depend upon telescopes to study and observe them. 

What are Celestial Bodies?

The celestial bodies are the objects located outside the earth’s atmosphere, for example, Moon, Stars, etc., further all the celestial bodies are classified into the following types.

1. Stars: 

Stars are the giant balls in space made of hot gases that can produce and illuminate their own light. Stars release energy by converting Hydrogen gas into Helium gas in their cores. Stars are giant in size and have an immense gravitational attraction force between them. The sun is a medium-sized star that gives us solar energy and makes life possible on earth.

2. Planets:

The planets are nearly large spherical objects that revolve around the sun. Planets move in the fixed orbits around the sun. There are 8 planets in our solar system. Planets may be made of rocks, metals and gases like hydrogen, nitrogen and methane. The earth is also one of the planets in our solar system and is the only known place in the universe that supports life. Planets that revolve around other stars are known as exoplanets.

3. Satellites:

Satellites are objects that revolve around the planets. They form an essential part of the celestial bodies. Satellites may be of natural origin or man-made known as the artificial satellite. The moon is a natural satellite of the earth, it revolves around earth because it is bound by the Earth’s gravitational pull.  Scientists also placed artificial or man-made satellites around the earth and other planets for various purposes and to study them in detail.

4. Comets:

Comets are the small pieces of ice and rock that come from the outer edge of the solar system. When the orbit of comets brings it closer to the sun, the ice on them vaporizes, creating a beautiful trail behind them. Hally’s comet was the most beautiful comet witnessed by human beings.

5. Asteroids:

The Asteroids are small irregularly shaped rocks made up of metal or minerals that orbit the sun. Most of the asteroids are found between Mars and Jupiter in the region known as the asteroid belt.

6. Galaxies:

Galaxies are large groups of stars held together by gravity. The sun and the solar system is part of a galaxy known as the Milky Way. Other galaxies are usually so far away that they look like stars in the night sky. The Andromeda galaxy and the Large Magellanic Cloud are galaxies that can be seen with the naked eye on a clear night.

Did You Know?

• There are around 400 billion stars in the galaxy and as many as 500 billion galaxies in the Universe.

• A dying star is called a White Dwarf. This happens when a star has burned up all of its nuclear fusion. It then turns into just a large clump that will emit light until it finally fades away.

NPN and PNP Transistors Definition 

Semiconductors are basically used in manufacturing two devices that are diodes and transistors. With the help of diodes, amplification of the signal is not possible and that is the reason we use transistors. In a transistor, one semiconductor is sandwiched from both sides by another semiconductor. The transistor has three regions that are emitter, base, collector. The emitter emits the charges and these charges are collected by the collector. Thee are two types of transistors NPN and PNP transistor. In PNP transistor they are two differences between both P, that is doping and the size of both p is different.

PNP Transistor Definition 

A transistor in which there is one n-type semiconductor that is doped by two p-type semiconductors from both sides is called PNP transistor. The PNP transistor turns on when there is no current at the base of the transistor.

In PNP transistors instead of electrons, the emitter emits holes and they are collected by the collector. Here the collector and the emitter old of p-type and the base are of n-type. The base size is small and it is lightly doped, the emitter size is moderate (between the base size and the collector size) and the doping is strong, collector size is large as compared to base and emitter and the doping is moderate (between the base and emitter doping). 

Symbol of the transistor is  

Here, which has an arrow is known as emitter, the base is always in the center. 

The arrow shows the direction of the electric current and the electric current always flows from positive to negative. To identify whether it is NPN or PNP we use this arrow.

If the arrow is pointing outside then it is NPN transistor and if it is pointing inwards then it is PNP transistor.

NPN Transistor Definition

A transistor, in which there is one p-type semiconductor that is doped by two n-type semiconductors from both sides are called NPN transistors. The NPN transistor turns on when the current flow through the base of the transistor. The current flows in the direction from the collector to the emitter. 

Usually, NPN transistors are used because it is easy to design them. In NPN transistors the majority charge carriers are electrons and in PNP transistors the majority charge carriers are holes. 

The mobility of electrons is better than the mobility of holes, therefore, NPN transistor works faster as compared to PNP transistors. So, we usually prefer NPN transistors for better results.

Transistor Action  

Each NPN junction has two terminals we connect a cell between them do there is a potential difference across it.

There is a rule for the emitter and the base that is the battery connected should always be in forward biased. And in the base and collector circuit, it is always reverse biased. 

In the above circuit diagram, the base terminal is common for the emitter and the collector so, therefore, it is called a common base configuration. Similarly, we can have a common emitter configuration and a common collector configuration.

But mostly we use a common emitter configuration because the most popular use of transistor is to make the amplifier and the best amplification is done by a common emitter configuration. Below is the circuit diagram of common emitter configuration.

After the circuit is connected the depletion layer of the emitter-base is decreased whereas the depletion region of the collector- base is increased.

The current flow is more in the emitter-base side current decreases in the collector- base side.

Resistance is decreased in the emitter-base side and becomes conductor, whereas resistance is increased in the collector-base side due to this the current majority stops in the collector-base side but the reverse current continues to flow.

The resistance is transformed from one side to another side; therefore, it is called a transistor.

More than 95℅ emitted electrons enter into the collector and only 5℅ recombine with the holes in the base, therefore, the collector current IC is much larger than the base current IB.

The transistor is also called a bipolar transistor because both the polarity carriers are present that are electrons and holes.

Solved Problems

1. In a collector-emitter connection, the current amplification factor is 0.9. If the emitter current is 1mA determine the value of the base current.

Solution- α = 0.9, IE = 1mA 

To find IB 

We know that,

α=IC / IE

IC= IE× α

IC= 0.9×1 = 0.9mA

Now, IE= IB +IC

IB= IE -IC

= 1-0.9

IB= 0.1mA

The base current is 0.1 mA.

2. In a collector base connection IE = 1mA, IC = 0.95mA. Calculate the value of IB.

Solution- We know that,

IE= IB + IC

IB= IE – IC

IB= 1 – 0.95

IB= 0.05 mA.

In physics, the study of objects is divided into mechanics. Mechanics have further been divided into two branches of study dynamics and statics. In the dynamic branch of mechanics, the particles in motion or the bodies in motion under forces’ action are studied. In this dynamics branch of mechanics, the study deals with bodies and objects that do not undergo any change in motion, that is they are moving at a uniform motion or are in equilibrium even with an application of force or torque. The dynamic mechanics is further divided into two parts for studying Kinetics and kinematics. They are also referred to as Kinetics Dynamics and Kinematics Dynamics. 

Kinetics Dynamics and Kinematics Dynamics

Often the terms Kinetics Dynamics and Kinematics Dynamics creates confusion in students’ minds more so because Kinetics is also a branch of study in chemistry and biochemistry that deals with the progress of reactions. Whereas the branch of Kinetics in Physics is entirely different from the one in chemistry, let us learn more about it and its differences. It is important to note that both Kinetics Dynamics and Kinematics Dynamics fall under one umbrella of Dynamics Mechanics. 

Kinetics and Kinetic Energy

Kinetics study deals with the movement of objects and that is due to kinetic energy and this can be classified into three different types. And this mainly deals with change in mass and velocity that will change depending on the type of object that is the mass of an object and the velocity of the change in motion due to force applied. Mass is represented as ‘m’ and velocity is represented by ‘v’. Even though kinetics has no specific formula the kinetic energy can be calculated using- 

Ek = ½ mv2

1. The rotational kinetic energy- this kind of energy is seen when the object is in the rotation of an object on an axis of the object. It is also called angular momentum or angular kinetic energy. The energy can also be possessed by the objects like the top moving in circles, or planets moving around the sun, so to study such objects in motion one has to use the method of rotational kinetic energy.

2. Vibrational Kinetic energy- Vibrational energy as the name suggests is possessed by objects which vibrate when a force is applied for example when phone rings and the other instance one can see is when one beats a drum it vibrates. 

3. Translational Kinetic energy- this kind of kinetic energy is seen when an object is already in motion and with a certain amount of force applied it moves from one place to another the energy force is transferred and translated as the change in velocity. 

Kinetics in Everyday Life

Kinetics and kinetic energy can be seen and experienced in our everyday lives as well. Certain examples are-

• It can be seen in hydropower plants, in here due to the kinetic energy of the water the plants can generate electricity.

• Generation of electricity with the help of windmills which are in motion.

• Moving cars possess kinetic energy.

• The motion of a bullet since force is applied via the gun possesses kinetic energy.

• Cycling as we apply force for the movement of pedals. Pedalling scents the bicycle in kinetic motion.

Conclusion

Kinetics is very important for the objects in motion or the dynamic objects. It has been an important mode of study in the field of physics ever since its discovery and is not subsiding anytime soon. We can find many answers to the questions of movement and mechanics through kinetics.