Tag: laws of reflection

Questions Related to laws of reflection

When a light ray falls on a perfectly reflective mirror at an angle. Identify which of the following statement is true about the ray?

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. The frequency of the light ray changes

  2. The wavelength of the light ray changes

  3. The velocity of the light ray changes

  4. The period of the light ray changes

  5. The direction of motion of the light ray changes

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Correct Option: E
Explanation:

When a light ray falls on a perfectly reflective mirror at some angle, then only the direction of the light rays changes such that the angle of incidence is equal to the angle of reflection but the frequency, wavelength, time period and the velocity of the light remain constant.

Thus option E is correct.

Identify on which of the following, specular reflection would most likely to occur. 

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. mirror

  2. wall

  3. sheet of paper

  4. ceiling.

  5. cat's fur

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Correct Option: A
Explanation:

The back of a mirror is usually covered with some sort of darkly colored, protective material to stop the silver coating from getting scratched, and also to reduce the risk of any light seeping through from behind. Silver reflects light better than almost anything else and that's because it gives off almost as many light as fall on it in the first place.

In which of the following conditions diffuse reflection takes place?

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. When a parallel beam of light is reflected by a plane mirror.

  2. When a parallel beam of light is reflected by a highly polished metal surface.

  3. When a parallel beam of light is reflected by a paper sheet.

  4. All of these

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Correct Option: C

A person has a $18$cm wide face and his two eyes are separated by 8 cm.Find the minimum width of a mirror required for the person to view is face laterally is

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. $9$cm

  2. $4$cm

  3. $5$cm

  4. $13$cm

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Correct Option: C
Explanation:

For minimum width -

i). Center of face and mirror must lie in perpendicular bisector of the line joining two eyes.
ii). Left eye must see right end point of face at the end of the mirror.
iii). Night eye must see left end point of face at then end of the mirror.
Now let, 
$F _1,F _2$ end points of face width $11E _1,E _2$ two eyes $11C-$ center of face.
$m _1.m _2-$ mirror end points
$m _1,m _2-$ projection of $m _1m _2$ on line joining two eyes.
Now, line joining two eyes should look like -
$F _1--E _1---m _1-C---m _2----E _2---F _2$
Due to symmetry,
$\Rightarrow F1E2=E1F2=13cm$
Also, $m _1,m _2$ must be midpoint of $F1E2$ and $E1F2$ respectively.
So, $E1m2=m1E2=\dfrac{13}{2}=6.5$
$E1m2=6.5$
$\Rightarrow E1C+Cm2=6.5$
     $4+Cm2=6,5$
     $Cm2=2.5$
similarly $m1C=2.5$
$\Rightarrow m1m2=m1C1C2=5cm=$ mirror width.
Hence, the answer is $5cm.$

A beam of light converges at point $P$. Now, a plane mirror is placed $20 \mathrm { cm }$ before the converging point $P$. The new converging point is

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. $20 \mathrm { cm }$ infront of the mirror

  2. $20 \mathrm { cm }$ behind the mirror

  3. The separation between new converging point and previous converging point is $40 \mathrm { cm } $

  4. None of the above

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Correct Option: A

The deviation produced by the first plane mirror during the first reflection is

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. $\delta _ { 1 } = 0 ^ { \circ }$

  2. $\delta _ { 1 } = 100 ^ { \circ }$ clockwise

  3. $\delta _ { 1 } = 100 ^ { \circ }$ anticlockwise

  4. $\delta _ { 1 } = 280 ^ { \circ }$ clockwise

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Correct Option: A

What is the correct definition of reflectance?

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. Difference between amount of light absorbed by the surface and amount of light reflected.

  2. The amount of light reflected by a surface is known as reflectance.

  3. The ratio of the amount of the light reflected from a surface to the amount of light falling on the surface is called reflectance.

  4. The ratio of amount of light falling on a surface to the amount of light reflected on the surface is called reflectance.

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Correct Option: C
Explanation:

According to definition, ratio of the amount of light reflected from a surface to the amount of light falling on the surface is called reflectance.

The angle formed between the incident ray and the normal is called _____________

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. angle of incidence

  2. angle of reflection

  3. angle of refraction

  4. none of the above

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Correct Option: A
Explanation:

Angle of incidence is the angle between incident ray and normal to the reflecting surface at the point of incidence.


Answer-(A).

When light rays travelling from one medium fall at the surface of another medium ............ the light rays returns back to the same medium.

physics reflection of light and shadow terms related with reflection terms related to reflection of light laws of reflection

  1. All of

  2. Part of

  3. None of

  4. Can't be determined

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Correct Option: B
Explanation:

When light rays traveling from one medium fall at the surface of another medium part of the light rays returns back to the same medium.
For example in window mirror we can see our image and we can also see outside objects because of both reflection and refraction of light.