Q: Change in the direction of light when it passes from one medium to another is called ............

\$ \bf{Reflection} \$ is the phenomenon in which light rays on striking a polished surface(such as a mirror) bounce back or are sent back into the same medium. \$ \bf{Refraction} \$ of light is the phenomenon of bending of light or change in the direction of light, when it passes obliquely from one transparent medium to another.\$ \bf{Diffraction} \$ is the phenomenon of bending of light waves around the corners of an obstacle or aperture, placed in the path of light beam. \$\bf{Scattering} \$ is the phenomenon by which a beam of light is redirected or deflected in many different directions when it passes through an imperfect medium due to the interaction with the particles of the medium.Hence, the correct answer is OPTION B.

Q: What is refraction? Give its two examples.

When travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as refraction of light. Refraction of light is accompanied by a change in speed of light at the interface of two optical medium.The two common examples of refraction are:A pencil immersed in a glass of water appears bent at the interface of water and air.A coin at the bottom of the vessel filled with water appears slightly raised above its actual position due to refraction of light.

Q: A coin kept in a container and not visible can be viewed by pouring water into the container. It happens because of the

When water is poured then it is due to refraction of light the coin becomes visible. When the light rays travel from the water medium (denser) to the air medium (rarer) it bends away from the normal due to the refraction. Therefore, an image of the coin is formed at a smaller depth causing it to be visible (as shown in the figure).

Question 1

Explain why the planets do not twinkle.

Accepted Answer

Hint: The planets are very close to earth in comparison to stars.Part 1: Size of appearing,$\bullet$The planets are very close to the earth comparative to the stars. $\bullet$Therefore the planets do not look like just a point in a the sky while they appear as a tiny disc of light while the stars appear as a point.Part 2:Conclusion,$\bullet$As the stars appear as the points in the sky, for very small angular displacement in the angular change in their image to the observer due to the variable air index makes them twinkling while the planets are tiny discs, hence they do not show the shift in their image so easily. $\bullet$Therefore planets show stability in their image and they do not twinkle.

Question 2

If a ray of light goes from a rarer medium to a denser medium , will it bend towards the normal or away from it ?

Accepted Answer

Refraction is the bending of light rays after entering a medium where its speed is different. Due to refraction of light, when a ray of light passes from a rarer medium to a denser medium, bends towards the normal to the boundary between the two media. The amount of bending depends on the indices of refraction of the two media. Hence, when a ray of light from air enters a denser medium, it bends towards the normal.

Question 3

When a ray of light passes from a rarer to denser medium it bends towards the normal. (True=1 or false=0).

Accepted Answer

Laws of refraction;-The incident ray,the refracted ray and the normal to the refracting surface at the point of incidence lie in the same plane.For a given pair of media and for a given colour of light the ration between the sine of angle of incidence to the sine of refraction is a constant.This constant is known as refractive index of the second medium with respect to the first medium.When a ray of light passes through a glass slab, $\angle i, \angle r$ and the normal all lie in the same plane.When a ray of light passes from one medium to another, here from air to glass or glass to air, the ratio $\frac{sin i}{sin r}=constant$.

Question 4

Change in the direction of light when it passes from one medium to another is called ............

Accepted Answer

$ \bf{Reflection} $ is the phenomenon in which light rays on striking a polished surface(such as a mirror) bounce back or are sent back into the same medium. $ \bf{Refraction} $ of light is the phenomenon of bending of light or change in the direction of light, when it passes obliquely from one transparent medium to another.$ \bf{Diffraction} $ is the phenomenon of bending of light waves around the corners of an obstacle or aperture, placed in the path of light beam. $\bf{Scattering} $ is the phenomenon by which a beam of light is redirected or deflected in many different directions when it passes through an imperfect medium due to the interaction with the particles of the medium.Hence, the correct answer is OPTION B.

Question 5

An under-water swimmer cannot see very clearly even in absolutely clear water because of:

Accepted Answer

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Question 6

Explain the following : The sun is seen before the sunrise and after the sunset.

Accepted Answer

EARLY SUNRISE and SUNSET : At sun Rise : When the Sun is just below the horizon , the light from the Sun suffers refraction from RARE to DENSER medium (As atmosphere is warmer than layers near the earth at that time) bends towards the normal at each refraction. Due to continuous bending of light rays, the Sun can be seen even when its actual positions just below the Horizon . As a result the Sun is seen in advance , two minutes before it rises above the horizon in the morning . Similarly , in the evening Sun is seen delayed by $2$ minutes longer above the horizon after the Sun set.

Question 7

The bending of light as it passes from one medium into another is commonly known as

Accepted Answer

In refraction ray of light passes from one medium to another medium. The ray of light bends towards normal in the denser medium.

Question 8

What is refraction? Give its two examples.

Accepted Answer

When travelling&#10;obliquely from one medium to another, the direction of propagation of&#10;light in the second medium changes. This phenomenon is known as&#10;refraction of light. Refraction of light is accompanied by a change in speed of light at the interface of two optical medium.The two common examples of refraction are:A pencil immersed in a glass of water appears bent at the interface of water and air.A coin at the bottom of the vessel filled with water appears slightly raised above its actual position due to refraction of&#10;light.

Question 9

A coin kept in a container and not visible can be viewed by pouring water into the container. It happens because of the

Accepted Answer

When&#10;water is poured then it is due to refraction of light the coin becomes visible. When the light rays travel from the water medium (denser) to the air medium (rarer) it bends away from the normal due to the refraction. Therefore, an image of the coin is formed at a smaller depth causing it to be visible (as shown in the figure).

Question 10

The apparent flattening of the sun at sunset and sunrise is due to

Accepted Answer

The apparent flattering of the sun at sunset and sunrise is due to refraction, because the sun becomes visible a little before actual sunrise and remains visible a little after actual sunset. because of atmosphere refraction of light.

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