Category: Physics Notes PPT

The Pinhole camera is the elementary camera that doesn’t have a lens, however it comes with a small aperture, and has a light-proof box with a small hole on one side. The light from the object goes through the aperture and it projects the inverted image on the opposite end of the box, which is known as camera obscura effect. 

Ibn Al-Haytham, an Arab scholar, was one of the first persons to demonstrate how we see, and for that purpose Al-Haytham came up with camera obscura, which is the predecessor to pinhole camera. He provided a demonstration on how light is able to project the image on a flat surface. Some of the materials that you require in the making of the pinhole camera includes aluminum foil, tape, paper clip or pin, and two pieces of the white cardstock.

 

Principle of pinhole camera

The principle of pinhole camera, also referred as camera obscura, is as follows. 

• The image that is formed by the pinhole camera displays rectilinear light propagation which means pinhole cameras work on the theory that light moves in the straight line.

• When the window or shutter is opened, the light illuminates thus forming the image on the film or photographic paper, which is placed on the back side of the camera.

 

Construction of pinhole camera

If you want to construct the pinhole camera then you must follow these steps.

1) Cut a square hole at the center of one of the pieces of the white cardstock. Next you must tape a foil on the hole. 

1. Now cut a square-shaped aluminum foil and then tape it on the cardstock hole.

2. Make a hole on the foil and use a pin or paper clip for prodding the hole in aluminum foil. 

3. Now place a second piece of the cardstock on the turf and hold it with the aluminum foil facing up above it.

4. Next view projected image appearing on cardstock below with the sun behind your back.

5. The farther the camera is held, the bigger the projected image becomes.

6. To have the projection more outlined, you can place the bottom piece of the cardstock in the area covered by shadow while the other piece is held in sunlight. You can explore by making different holes in the foil, thereby making distinct patterns, shapes and designs. 

Uses of pinhole camera

• The pinhole camera is utilized for projecting the specific image on the translucent surface and this facilitates the safe as well as real-time observation of the solar eclipse. 

• These cameras can be used for surveillance since they are hard to detect.

• The pinhole camera can be used for observing reflected images of glittery objects like the sun.

• Most of the applications make use of pinhole camera models for the study of sun’s movement over a lengthy period of time. This process is called solargraphy. 

We all deal with a graph, mark a line from the origin and reach the other end till out requirement. All these requirements are done on the coordinate system. So, the coordinate where our line indicated by an arrow terminates is the coordinate of this ray. 

Let’s consider, you started your journey from home to reach your favorite destination and then route to another destination, so your arrow is changing both of its length and direction, which means your position vector is changing and in case, you choose the shortest path, i.e., displacement, you represent it by the displacement vector.

Position Vector Definition

We define the position vector as a straight-line having one end fixed to an object and the other end attached to a moving point (marked by an arrowhead) and used to represent the position of the point relative to the given object. As the point moves, the position vector changes in length or in direction, and sometimes both length and direction change.

An Introduction to Position Vector and Displacement Vector

In the study of our physical world, the concepts of position and displacement are the foundational topics for the chapter of motion. The concept of ‘or ‘position vector’ has been adopted from Euclidean spaces or geometry and is also known as location vector or radius vector. The position of any point in space is expressed in terms of three coordinates, namely ‘x,’ ‘y,’ and ‘z’ distances from any arbitrary point denoted as ‘O’ or origin. The straight line from origin to the point is denoted by ‘r’ or ‘s’.  In Physics this vector is used while describing an object in rest or in motion in space with reference to another object. depending upon the various locations at different instants of time the vector changes in length and direction accordingly. 

The three coordinates described in vectors of each direction are also referred to as three dimensions. Displacement is any change in any of these vectors. In common language, we know displacement as any movement of an object from one place to another place by following a straight path. If any object doesn’t follow a straight line path then the total path covered is measured as distance. And the displacement in this case would be the straight distance between the starting point and finishing point. While describing a displacement, which informs the shortest distance between two points, it is also important to mention the direction of the displacement to know the exact location of the final point. Thus when we denote the direction of a point then it is known as position vector and when the direction of a displacement is mentioned then it is known as displacement vector.

What is Position Vector?

In the above statement, we took a coordinate system to represent your journey from the origin, i.e., your home to reach your favorite destinations, first, Darjeeling, then, Karnataka.

Each destination is marked by an arrow on the graph, which changes or varies as you change your destination, below is the graph to represent the same:

Hence, your position vector changes,  i.e, two times or twice the length, and the direction of the position vector changes according to this scenario.

So, along the X-axis, the position vector is: ‘i (cap)’ and along the Y-axis, it is ‘j (cap)’. Since the position vector sum is represented by r[^{rightarrow }], so the vector sum of the position vectors along the coordinate axes will be as follows:

r[^{rightarrow }] = i (cap) + j (cap)…..(1)

Displacement Vector Definition           

A displacement vector is one of the important concepts of mathematics. It is a vector. It represents the direction and distance traveled by an object in a straight line. We often use the term ‘displacement vector’ in physics to showcase the speed, acceleration, and distance of an object traveling in a direction relative to a reference point or an object’s starting position.

What is a Displacement Vector?

The displacement vector definition is very simple to understand. Let’s discuss the scenario, you decide to travel to two locations for office work in the minimum time possible, and both of these locations are adjacent to each other in the mid of two roads passing opposite each other. Now, you have to decide from which path you should go in order to reach in the required time, as there is a lot of traffic on the road and the thoughts of getting scolded by your boss. So, below is the visual schematic representation of your situation:

So, here, the green line is the shortest path, which will help you reach the middle of the two roads and reach the two locations on time. So, a displacement vector represents the minimum distance to reach on time rather than taking a long path with a wastage of a large amount of time.

Now, after your work is done, you take an opposite oath, so here, your displacement isn’t changing, only the direction is. So, with the direction, the displacement vector changes in terms of direction, not in magnitude. 

Displacement Vector

We know that the change in the position vector of an object is known as the displacement vector. Let’s suppose that an object is at the point P at time = 0 and at the point Q at time = t. The position vectors of the object at the point P and at point Q are represented in the following way:

Position vector at point P = r[^{rightarrow }] P (cap) = 8i (cap) +5j (cap) + 3k (cap)….(a)

Position vector at point Q = r[^{rightarrow }] Q (cap) = 2 (cap) +2j (cap) +1k (cap)…..(b)

Now, the displacement vector of the object traveling from time interval 0 to t will be as follows:

r[^{rightarrow }] Q (cap)−r r[^{rightarrow }] P (cap) =− 6i (cap) − 3j (cap) −2k (cap)….(c)

Equation (c) is the displacement vector formula and the schematic representation of this equation is as follows:

We can also define the displacement of an object as the vector distance between the initial point and the final/ultimate point of the destination. Suppose an object travels from point P to point Q in the path shown in the black curve:

We can imagine that the displacement of the particle would be the vector line PQ, headed in the direction P to Q and the direction of the displacement vector is always initiated from the initial point and terminated to the final point.

The Final Words

One of the most important aspects of kinematics is the position vector and the displacement vector; also, the key differences between these two, about which we discussed in the above context. 

The position vector specifies the position of a known body. Knowing the position of a body is paramount when it comes to describing its motion. However, the change or variation in the position vector is the displacement vector.

The earth atmosphere has a pressure system that is particularly high or low compared to the air surrounding it. Air expands when noted and gets compressed when cooled. This results in atmospheric variations. Due to the difference in atmospheric pressure, air now starts moving from high pressure to low pressure. The movement of the wind is horizontal, and thereby a constant temperature is maintained on the planet. Pressure systems of the earth are widely divided into two parts: High-pressure system and the low-pressure system. The weather of an area is determined locally by the pressure system. Low-pressure systems bring about clouds and rain while high-pressure systems are responsible for clear skies. 

Explain The High-Pressure System 

The high-pressure system is relative to the air around it. As the air starts becoming warm or cold, it can be said that a high-pressure system has been created. The high-pressure system is composed of air that is heavy and cool. In the high-pressure system, the air is not rising and forming clouds. Therefore the weather remains comfortable, and skies stay clear. In the Northern Hemisphere, the high-pressure system revolves in a clockwise direction, while in the Southern Hemisphere it is in the anti-clockwise direction. 

Explain The Low-Pressure System 

A low-pressure system, commonly known as depression, is created in an area of warm air. As we all know, warm air rises, and cold air falls. The low-pressure system rotation is in the clockwise direction in the Southern Hemisphere and in the opposite direction in the anti-clockwise direction in the northern hemisphere. A low-pressure system brings about heavy rainfall. Depression can often mature into a cyclonic storm in case the low pressure persists. Over the Atlantic Ocean, during the autumn season, the low-pressure system increases, bringing with it windy weather, rain, storms and heavy thundershowers. 

Features of Atmospheric Pressure 

• Atmospheric pressure indicates weather conditions of an area. 

• Low pressure causes cloudiness, thunderstorms, storms and cyclonic winds.

• High pressure contributes to calm weather conditions. 

• An instrument known as the barometer measures atmospheric pressure. Therefore the barometer is also known as barometric pressure. 

• One atmosphere is 1013 millibars or 760 millimetres. 

The atmospheric pressure is an important environmental factor. It affects all the three states of matter that are solid, liquid and gas. This atmospheric parameter has been used quite a number of years to predict weather conditions all over the world. The composition of water and its chemistry is also affected by atmospheric or barometric pressure. The earth’s atmosphere has five layers. From highest to lowest they are:

1. Exosphere

2. Thermosphere 

3. Mesosphere

4. Stratosphere 

5. Troposphere 

Each of these layers extends up to an absolute mile and are above sea level. The exosphere is about 700 km above sea level while the average height of the troposphere is near about 18 km in the tropical regions and 6-7 km in the polar region. In various images, the different atmospheric layers are shown in different colours. Each of these layers has a different temperature and pressure levels. 

Solved Examples

1. Difference between High and Low Pressure Systems.

A low-pressure system has slight pressure in the area of the suit and its centre. The wind blows towards the low-pressure areas, and the air rises in the atmosphere as soon as they meet. Once the air rises, clouds are formed, leading to precipitation. On weather maps and meteorological departments, a low-pressure area is marked with an L. 

A high-pressure system has pressure in its centre and the surroundings. In a high-pressure system, the winds blow in an anticyclonic manner. This results in the air from the higher atmosphere to fill the spaces left in the outward. On a weather map, you might notice a high-pressure system marked as H. 

Fun Facts

• The readings of a pressure system are given in millibars. 

• Places having equal air pressure are connected by lines known as Isobars. Sea level pressure has an average of around 1013 millibars. 

• Any changes in the air pressure will accordingly determine the weather of a localised area. 

• As air pressure increases the weather becomes clearer while falling air pressure leads to storms.

• Pressure readings are usually relative to that of the area. There is no scale or division of the air pressure range. 

An earthquake is basically the shaking of the surface of the earth that is caused due to the sudden release of energy in the lithospheric layer of the earth’s surface. The sudden release of energy in the lithosphere creates seismic waves and these waves are the cause of earthquakes. These earthquakes differ in their magnitude. Their range varies greatly, it can be so small that it cannot be even felt or it can be such a large range that it can cause objects or even person propels themselves into the air. Such earthquakes are extremely violent and can cause destruction to the whole city or area. If we talk about seismicity. Seismicity is actually the frequency, size, and type of earthquake that is experienced by a city or a place over a period of time.

On the surface of the earth, earthquakes manifest themselves by shaking the grounds causing the displacing or disrupting of the ground. If the earthquake is a large one then its epicenter will be located at the seashore. In this case, the seabed may be shifted and a tsunami can be caused in such cases. Now, these earthquakes can also cause landslides in the hilly areas and these landslides are the major cause of accidents in the hilly areas. Occasionally, volcanic eruptions are also caused by these earthquakes.

If we talk about earthquakes in the most general way then it is all about seismic events. These earthquakes can be natural or can be caused due to various human activities that nowadays are causing a great shift in an environment only in the negative side  Earthquakes are mostly caused by geological faults, volcanic eruptions, mine blasts, landslides, nuclear tests and so in. The initial point of rupture of an earthquake is known as its hypocentre and just above the hypocentre lies the epicenter of the earthquake.

In this article, you will come to know about the earthquakes, the causes, and the way you can protect yourself from earthquakes and even prevent these earthquakes. Let us now have a look at the article to get a better understanding of earthquakes.

Protection Against Earthquake

Earthquake: A term which is an earthquake is also known as a quake in normal use or tremor or tremblor it is said so because of the shaking of the surface. The term that is seismicity or seismic activity we can say which is of an area is the frequency and the type and size of earthquakes as well which is experienced over a period of time. The word tremor is sometimes also used for non-earthquake seismic rumbling.

Prediction of Earthquakes 

The branch that deals with the prediction of earthquakes is known as seismology. This study is concerned with the specifications, such as the time, magnitude, location of further earthquakes that will occur in the future but within the stated limits only. Many different kinds of methods were discovered in order to predict earthquakes but still after so much effort also the seismologists are not able to find the exact scientific method for predicting earthquakes.

Protection Against Earthquake

In minutes or we can also say the hours and days that are after an earthquake that our neighborhood and community may experience ground shaking and along with that some damage that is in the buildings and landslides and fires that is we can say possibly tsunamis if we are on the coast. The best way to avoid injuries from this damage is to keep in touch with our loved ones and recover swiftly from an earthquake is to prepare now for how we and our family will respond when an earthquake strikes.

For help in protecting our home and belongings too during and after an earthquake so we can say that please we should see what we can do on the page.. For the basic information which is about earthquakes and the hazards which are related.

In case of the emergency management agencies which are in British Columbia, California and then Oregon and Washington and the Federal Emergency Management Agency that is the full form of FEMA and some county and other local agencies provide earthquake resources which is to help us know what to do before and during and after an earthquake. These actions include the following:

Before the Dangerous Earthquake

We need to prepare to be on our own for at least three days with a disaster supply kit which includes water and the non-perishable food and the first aid materials as well and along with that copies of important family documents.

To know how to turn off utilities also.

We have often heard that prevention is better and hasn’t been cured so if we are already having these prevention e measures it will be easy for us to keep ourselves protected from hazardous earthquakes.

Usually, for building owners, their US earthquake insurance is provided to them that will enable them to get financially protected at such crucial times.

Earthquake management strategies can be prepared by the government in order to be prepared for the consequences of these earthquakes.

At this time artificial intelligence may help, just by getting access to the building, and along with it precautionary methods can be planted by them.

Individuals can also play their part in precautionary methods, they can secure water heaters or other heavy matter that may cause serious damage to the people around.

During the Earthquake

We can use the formula of  Drop and the cover and hold

• If we are inside when we feel the ground shake we need to drop down to the floor.

• Then we can take cover that is under a sturdy piece of furniture or seek cover against it. That is we can say an interior wall and protect our head and neck with our arms. We can then avoid the dangerous spots that are near the windows which are hanging objects and then the mirrors or tall furniture. We can say that we can hold the position until the ground stops shaking and it is safe to move.

• If we are somewhere outside to get into the open then away from buildings and away from the power lines and trees as well. We should be alert for falling rocks and other debris that could be loosened by the earthquake.

• One thing that you should remember is that you are not required to panic. You may have precautionary measures, try to follow them in such hard situations, besides this you need to work safely that we try to vacate the building and get outside from any building along with this make sure all the sweet he’s and gas stove, etc are closed or turned off in order to protect yourself from getting any type of major injury

Types of Earthquake 

The one which is naturally occurring.

We can say that the tectonic earthquakes that generally occur anywhere on the planet that is the earth where there is sufficient stored energy are the elastic strain which is of energy to drive fracture propagation along a plane that is at fault. We can here say that the sides which are at fault move past each other too very smoothly and seismically only if there are no irregularities or we can say that only if asperities along the fault surface increase the frictional resistance. Here we can say that most fault surfaces do have such asperities which leads to a form of stick-slip behaviour. 

There are many different types of earthquakes that are named as the tectonic and then the volcanic, and explosion. The type of earthquake generally depends on th
e region where it occurs and the geological make-up of that region. We can see here that the most common are tectonic earthquakes. These earthquakes occur when rocks in the planet that is on earth’s crust break due to geological forces created by the movement of tectonic plates. Another type of disaster is volcanic earthquakes which generally occur in conjunction with volcanic activity. We can also generally measure motion from large tectonic earthquakes using GPS because the rocks which are on either side that are of a fault are offset during this type of earthquake.

Those people who work with or around radiation, one of the most important factors is an awareness of the levels of radiation around them. This is primarily accomplished through the use of radiation detectors of varying types. 

How do you define the terminology radiation detector? Simply, a Radiation detector or a particular detector is a device used to detect, track, or identify ionizing particles, such as those produced by cosmic radiation, nuclear decay, or reactions in a particle accelerator. Radiation detectors can measure the particle energy and other attributes such as momentum, spin, charge, particle type, in addition to merely registering the presence of the particle.

Evolution of Radiation Detector

In the early days, photographic plates were used to identify tracks left by nuclear interactions. A photographic plate would be placed in the path or vicinity of a radioactive beam or material. When the plate was developed, it would have fogged or spotted from the exposure to the radiation. Then the sub-nuclear particles were discovered using cloud chambers, which needed photographic recordings and a tedious, complicated measurement of tracks from the photography.

Another commonly used radioactive detector in the early days was the electroscope. These used a pair of gold leaves that would become charged by the ionization caused by radiation and repel each other. This process provided a means of measuring radiation with a better sensitivity level than was reliably possible using photographic plates. Depending on the arrangement of the device, they could be configured to measure alpha or beta particles and were a valuable tool for early experiments involving radioactivity.

Another interesting early device, invented out of a desire to measure the actual individual particles or rays being emitted by a radioactive substance, as opposed to a more gross measurement of a dangerous field, was the spinthariscope.

Developed by William Crookes, who had also invented the Crookes Tube used by Wilhelm Roentgen to discover X-Rays, it used a zinc sulfide screen at the end of a tube and a lens at the other end, with a small amount of a radioactive substance near the zinc sulfide screen. The zinc sulfide would react with the alpha particles emitted, and each interaction would result in a tiny flash of light.

This was one of the first means of counting a rate of decay, albeit a very tedious one, as it meant scientists had to work in shifts watching and literally counting the flashes of light. The spinthariscope was not very practical as a long term Radiation detection, though it did undergo a revival later in the 20th century as an educational tool.  The tendency of certain materials to give off light when exposed to radiation would also prove valuable in future radiation detection technologies.

Electronic detectors were developed with the invention of the transistor. Modern detectors use calorimeters to measure the energy of the detected radiation. They may also be used to measure other attributes of the particles.

These early used devices, and many others, such as cloud chambers, played a valuable role in understanding the basic principles of radiation and conducting important experiments that set later scope development. This included the development of new types of radiation detectors, many of which are still in use today, such as ion chambers, G-M Tubes, and Scintillators. 

Types of Detectors

There are various types of detectors that are in use. Some of them are:

Scintillation

One of the significant types of detectors utilized in radiation detection instruments is Scintillation Detectors. Scintillation is the act of giving off light. For radiation detection, some material can scintillate when exposed to radiation that makes them useful as detectors. Each of the photon radiation that interacts with the scintillator material will result in a distinct flash of light, meaning that in addition to being highly sensitive, scintillation detectors capture some specific spectroscopic profiles for the measured radioactive materials.

When a scintillator is coupled to an electronic light sensor such as a photodiode, photomultiplier tube (PMY), or silicon photomultiplier, a scintillator detector, scintillator-type detectors use a vacuum and first convert light into electrical pulses.

Gaseous Ionization Detectors

A radiation detection device which is used to detect the presence of ionizing particles, and in applications which are radiation protected to measure ionizing radiation is called Gaseous ionization detectors.

There are other types of gas-filled detectors such as proportional counters, and Geiger-Mueller (G-M) tubes. The major differentiating factor between these different types is the applied voltage across the detector, which determines the kind of response that the detector will register from an ionization event.

Geiger Counter

Geiger counter is an instrument that measures or detects ionizing radiation. It is also known as Geiger -Muller counter. It detects ionizing radiation such as alpha particles, beta particles, and gamma rays.

Given the mysterious beauty of the boundless cosmos, there’s no doubt that telescopes are in the middle of the most fascinating instruments in the field of science. 

 

Telescope

The word ‘Telescope’ was coined by Giovanni Demisiani in 1611. 

 

Telescope, is an instrument used to form magnified images of distant particles. The first telescope’s invention is a bit hazy. A telescope is an optical device that observes distant objects using lenses, curved mirrors, or a combination of the two. It may also be used to observe distant objects using electromagnetic radiation emission, absorption, or reflection.

 

The first practical telescopes were refracting telescopes with glass lenses, which Galileo discovered in the Netherlands at the beginning of the 17th century. The telescope is the most important research tool in astronomy. Telescopes enable you to absorb and analyse radiation from astronomical phenomena, including those that are far apart in the cosmos.

 

Eyeglass-makers had been experimenting with lenses before 1600. The first mention of a telescope happens in a letter written in 1608, by Hans Lippershey, who was a Dutch spectacle maker in the process of seeking a patent for a telescope. The patent was denied because of easy telescope duplication, and  there was difficulty in the process of patent enforcement. The instrument spread very rapidly. Galileo made sense of it in the early 1600s, and he made improvements in lens grinding that did increase the magnification from a relatively low value of two to as much as thirty. With these powerful telescopes, he made observations in the Milky Way, of the mountains on the Moon, the phases of Venus, and the moons in the planet Jupiter. These early telescopes were a type of ‘opera glass,’ which produced erect or right side up images. But they had very limited magnification. When Johannes Kepler, who was a German mathematician and astronomer working in Prague under Tycho Brahe, heard of Galileo’s discoveries, he perfected a more different kind of telescope. Kepler’s design inverts the image in general , it is much more than everything else.

 

The reflecting telescope makes use of mirrors to collect and focus light. Telescope now implies the diverse range of instruments that are capable of detecting various regions of the electromagnetic spectrum

 

In the twentieth century, new types of telescopes were discovered, including radio telescopes in the 1930s and infrared telescopes in the 1960s. Let’s discuss the types of telescopes and their names.

 

Types of Telescope

1. Optical telescopes

2. Radio telescopes

3. X-ray telescopes

4. Gamma-ray telescopes

As we know there are different types of telescope available for different observations. Here, we will discuss optical telescopes and their types.

 

Optical Telescopes

An optical telescope converges and focuses light mostly from the visible part of the electromagnetic spectrum (while some work in the infrared and ultraviolet). Optical telescopes increase the observed angular size of distant objects along with their observed brightness.

 

An optical telescope creates a magnified image for direct view, or to make a photograph, also for collecting data through electronic image sensors.

 

 

Telescopes use one or more curved optical components, normally made of glass lenses and mirrors, to collect light and other electromagnetic radiation and carry it to a focal point, allowing the image to be viewed, photographed, analysed, and sent to a device.

A telescope is used in many non-astronomical instruments as well as in astronomy, including theodolites, spotting scopes, monoculars, binoculars, camera lenses, and spy glasses. Optical telescopes use polished mirrors or glass lenses to focus observable light as it comes in through the hole. The word is most often applied to a monocular with a fixed mount for observing the sky and handheld binoculars are widely used for a variety of purposes.

 

There are Three Main Optical Telescope Types: reflecting and refracting telescopes.

Please observe the following image, the difference between reflecting and refracting is represented easily.

 

 

Refracting Telescopes

A refracting telescope is also called a refractor telescope.  This telescope is a type of optical telescope that uses a lens as its main purpose is to form an image. This telescope is used in spy glasses and astronomical instruments, as well as it is used for long-focus camera lenses. The magnification of a refractor is measured by measuring the focal length of the object lens by the focal length of the telescope’s eyepiece.

 

A lens is usually at the front, followed by a long tube, and then an eyepiece or instrumentation at the back, where the telescope image is brought into focus. The diameter of the design is referred to as the hole its ranges from a few centimetres for small spotting telescopes up to one meter for the largest refractor in existence. The design, as well as the eyepiece, may have specific components. Small spotting telescopes may contain an extra lens in the back of the eyepiece to erect the image so that it does not appear upside-down.

 

 

However, refracting telescopes is very common in the second half of the nineteenth century, reflecting telescopes have since replaced them for more scientific purposes, as they allow for a larger hole.

 

Telescopes which make use of the refractive property of lenses are called refractors. If a refractor has a large light-gathering power (a necessity for astronomical observations), the lenses should be quite large. The instrument at the Yerkes Observatory has an objective lens with a diameter of 1 m. Lenses of such size are tough to manufacture. They have great weight and are subjected to cracking due to temperature changes. For these reasons, large diameter refractors are not practical instruments. Very few of them are still in use for astronomical research operations.

 

Difference Between Reflectors and Refractors

Refractor telescopes use specialized lenses that make them a favourite for deep space objects like galaxies. On the other hand, reflector telescopes are more popular with larger and brighter objects like the moon and planets. Refractors telescopes utilize specially designed lenses to focus the light on an image. A Reflector telescope uses mirrors, which causes light to reflect at different angles within the optical tube and extends the overall light path. Reflecting telescopes have many advantages as compared to refracting telescopes.  The reflector telescope price is cheaper to make than refractors of the same size. Because the light is reflecting off the objective, compared to passing through it, only one side of the reflector telescope’s objective needs to be perfect. Hence the reflector telescope price is less than the refracting telescope.

 

Reflecting Telescopes

A reflecting telescope is also called a reflector. It works by using signals or a collection of curved mirrors to reflect light and create an image. In the seventeenth century, a reflecting telescope was discovered by sir Is
aac Newton as a replacement for the refracting telescope, at that time, was a design that had a lot of chromatic aberration on it.  The telescope design allows for very large diameter objectives. Since the mirror is used in telescope, the design of the telescope is referred to as a “catoptric” telescope. It is a telescope that uses a combination of curved mirrors to reflect light and produce an image of a distant object. It is used to examine the visible region of the electromagnetic region as well as the shorter ( i.e ultraviolet) and longer (i.e infrared) wavelength regions adjacent to it. Reflecting telescope is so called because the primary mirror reflects the light to a focus instead of refracting it. The primary mirror is a concave spherical or parabolic shape and inverts the image at the focal plane. A secondary curved mirror which is in combination with an eyepiece, is used to observe the image.

 

 

Reflecting telescopes are extraordinarily popular for astronomy and many famous telescopes such as the ‘hubble space telescope’ and ‘popular amateur models’ use the design of the reflecting telescope. Besides, the reflected telescope concept has been extended to other wavelengths of light, and for example, x-ray telescopes also use the reflection principle to make image forming optics.

 

Let’s discuss some reflecting type telescopes and their major differences. These include the Newtonian, Cassegrain, and schmidt-cassegrain telescopes.

 

Newtonian Telescope

Newtonian telescope also called the Newtonian reflector telescope. These telescopes are usually less expensive for any given objective diameter than any quality telescopes of other types. This telescope was invented by the english scientist sir isaac newton therefore the telescope is also called as isaac newton telescope. Since only one surface must be ground and polished to achieve a complex form, fabrication is much simpler than other telescope designs.

 

A short focal ratio can be more easily obtained and leads to a wider field of view.

 

Light approaches the telescope from the left side and hits the primary mirror at the back of the telescope. A focused image is bounced off of a secondary mirror, via an eyepiece, and to the observer’s eye. In a reflecting telescope, a secondary mirror focuses light from the main mirror to a different focal point. The eyepiece of a telescope is present at the top end of the telescope. Newtonian telescopes are generally cheaper as compared to the other telescopes with a similar configuration for any given aperture. The production of these telescopes is simple. They involve only one surface that requires ground. They get polished into a complex shape.

 

 

Cassegrain Reflector Telescope

The cassegrain reflector is a composition of a primary concave mirror and a secondary convex mirror. In a symmetrical cassegrain telescope, both mirrors are aligned about the optical axis, and the primary mirror generally contains a hole in the centre, thus enabling the light to reach an eyepiece, a microphone, or an image sensor. The cassegrain configuration uses a parabolic reflector as the primary and the hyperbolic reflector as a secondary mirror. 

 

In a cassegrain telescope, the primary mirror and secondary mirror both are curved. The light hits the concave primary mirror, which reflects the convex secondary mirror. The convex secondary mirror then reflects the light through a small hole in the concave primary mirror to the eyepiece. Hence the design allows the shorter tube relative to its mirror diameter because the telescope’s focal length is longer than the length of the tube.

 

Variations of cassegrain reflector telescopes:

Ritchey–Chrétien telescope

Dall–Kirkham telescope

Off-axis configuration

Schiefspiegler telescope

Yolo reflector

Catadioptric Cassegrains 

Schmidt-Cassegrain Telescope

Maksutov-Cassegrain Telescope

Argunov-Cassegrain Telescope

Klevtsov-Cassegrain telescope