Tag: reflection of light and shadow

Questions Related to reflection of light and shadow

 A beam of light passes through layers of following different substances each 10 cm thick normally. In which substance does the beam take more to pass through? 

physics reflection of light and shadow beam of light ray and beam ray optics

  1. Glass slab $(\mu =1.5)$

  2. water $(\mu =1.33)$

  3. Fibre slab $(\mu =1.65)$

  4. Alcohol slab $(\mu =1.36)$

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Correct Option: B

Sun rays on the surface of the earth

physics reflection of light and shadow beam of light ray and beam ray optics

  1. form convergent beam

  2. form divergent beam

  3. form parallel beam

  4. None of these

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Correct Option: C

A wave $ y = 10 sin (ax + bt) $ is reflected fron a dense medium at an origin. if 81% of energy is reflected thn the equation of reflected wave is :

physics reflection of light and shadow beam of light ray and beam ray optics

  1. y= sin -8.1 sin (ax - bt)

  2. y= sin 8.1 sin (ax - bt)

  3. y= sin -9 sin (ax - bt)

  4. y= sin 10 sin (ax - bt)

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Correct Option: B

If the angle of elevation of sun increases from ${0}^{o}$ to ${90}^{o}$ then what will be the change in length of shadow of tower?

physics reflection of light and shadow beam of light ray and beam ray optics

  1. No change in length of shadow

  2. Length of shadow increases

  3. Length of shadow decreases

  4. Length of shadow will be zero

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Correct Option: C,D
Explanation:

Length of shadow decreases and will be zero.
"Angle of elevation" is the angle between the thing being referenced and the horizontal. So, when the sun rises the angle of elevation increases and your shadow becomes shorter. When the sun is directly overhead, you don't have a shadow and the angle of elevation is 90, which is the greatest angle. So, the closer to midday, the shorter the shadow and the greater the angle of elevation.

In a room lighted by an electric bulb, it is found that the shadow of the ceiling fan hung in the centre is falling on a wall opposite to the door. What can you say about the position of the bulb? 

physics reflection of light and shadow beam of light ray and beam ray optics

  1. On the wall having the door

  2. On the wall facing the door

  3. On the wall on your right as you enter the room

  4. On the wall on your left as you enter the room

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Correct Option: A
Explanation:

Answer is A.

When we put any object in between the light source it forms a shadow of that object. The closer the object is to the source of the light, the more light it blocks out, so its shadow is bigger. But if the object is further away, it does not block out much light, and so the shadow is smaller.
Therefore, for the shadow of the ceiling fan to be formed on a wall opposite to the door, the electric bulb must be positioned on the wall having the door.

Which of the following statement is true?

physics reflection of light and shadow beam of light ray and beam ray optics

  1. All light is electromagnetic wave

  2. Electromagnetic energy is created only by heat

  3. Matter emits a single, unique photon when it is heated

  4. All of these

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Correct Option: A
Explanation:

Option A $\rightarrow $ All light is electromagnetic wave. This option is correct as EM light does not need any medium to travel like EM wave.

Option B $\rightarrow $ Electromagnetic energy created only by heat.
                    This option is false.
Electromagnetic energy can be created in any case of accelerated charge.
Option C $\rightarrow $ When matter is heated many photos are ejected.
                     So this option is false.

When all the parallel rays reflected from a mirror are parallel, the reflection is known as:

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. regular reflection

  2. irregular reflection

  3. diffused reflection

  4. none of these

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Correct Option: A
Explanation:

In regular reflection, parallel rays of light, after reflection, emerge as parallel.

Irregular reflection _______ laws of reflection.
physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. obeys

  2. violates

  3. obeys sometimes

  4. violates sometimes

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Correct Option: A
Explanation:

Irregular reflection always obeys laws of reflection.

You are able to see in shaded areas, such as under a tree, because light has undergone:

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. refraction

  2. incident bending

  3. a change in speed

  4. diffused reflection

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Correct Option: D
Explanation:

In a diffused or irregular reflection, parallel rays of light, after striking a rough and curved surface, get reflected irregularly.

Which surfaces are said to be smooth?

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. As long as the irregularities of surfaces are small as compared to the wavelength of the incident light.

  2. As long as surface irregularities are large compared to the wavelength of the incident light.

  3. As long as surface smoothness are small as compared to wavelength of reflected light

  4. As long as the surface irregularities are large as compared to the wavelength of reflected light.

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Correct Option: A
Explanation:

A surface behaves as a smooth surface as long as the surface irregularities are small compared with the wavelength of the incident light.