Tag: nature and sources of light

Questions Related to nature and sources of light

How are non luminous objects visible to eye ?

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. Non-luminous objects give away light

  2. Non-luminous objects reflect the light falling on them

  3. Non-luminous objects disperse the light falling on them

  4. None of the above

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Correct Option: B
Explanation:

Non-luminous objects reflect the light falling on them and the reflected light are sensed by the eye and thus we are able to see non-luminous objects.

When Abhishek looked at a lighted torch through an object he could see a faint glow, but not the torch. The object is

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. Transparent

  2. Opaque

  3. Translucent

  4. None of these

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Correct Option: C
Explanation:

Translucent objects allow only a small part of light to pass through them.

Read the given statements and select the correct option.
Statement 1 : Rahul placed a coloured plastic bottle in front of the beam of a torch light. Then he placed a transparent sheet of same size on the other side of bottle. No shadow will form on the screen.
Statement 2 : Translucent objects allow light to pass through them partially.

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.

  2. Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1.

  3. Statement 1 is true but statement 2 is false.

  4. Statement 1 is false but statement 2 is true.

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Correct Option: D
Explanation:

A coloured plastic bottle is an opaque material. When a light beam is incident on it, a shadow will form on the screen. Light can easily pass through the transparent material.

Which of the following statements is true?

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. The image formed by a pinhole camera is inverted because light travels in a straight line.

  2. Light does not change its direction on reflection.

  3. As we move the object away from the light source, the shadow of the object becomes smaller.

  4. Reflection is possible only from polished surface.

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Correct Option: A
Explanation:

Light changes its direction after reflection. As we move the object away from the light source, the shadow becomes larger as the distance between object and the light source increases. Reflection is possible from rough surface also.

We cannot see things in the absence of

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. Air

  2. Water

  3. Light

  4. Earth

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Correct Option: C
Explanation:

We can see things when rays of light coming from any object reach our eyes. So, we cannot see in the dark because of absence of light. 

Ray optics is valid when characteristic dimension are  

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. much smaller than wavelength of light.

  2. of same order as wavelength of light

  3. much larger than wavelength of light

  4. none of the above

Show answer
Correct Option: C
Explanation:

Ray optics is valid when characteristic dimension are much larger than wavelength of light . The size of obstacle must be much larger than the wavelength of light. If wavelength is comparable to the size of object, then diffraction could happen, but it cannot be explained using ray optics, it will require wave theory of light. 

The difference in speeds of a ray of light in glass and water is $2.5 \times 10^7 \,m/s$. If the $R.I$ of glass and water are $\dfrac{3}{2}$ and $\dfrac{4}{3}$ respectively, then the velocity of light in air is

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. $2 \times 10^8 \,m/s$

  2. $2.25 \times 10^8 \,m/s$

  3. $3 \times 10^8 \,m/s$

  4. $2.5 \times 10^8 \,m/s$

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Correct Option: B

Light travels through a glass plate of thickness t and refractive index $\mu $ If c is the speed of light in vacuum, the time taken by light to travel this thicknes of glass is 

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. $\mu tc$

  2. $\dfrac { tc }{ \mu } $

  3. $\dfrac { t }{ \mu c } $

  4. $\dfrac { \mu t }{ c } $

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Correct Option: C

It is necessary to illuminate the bottom of a well by reflected solar beam when the light is incident at an angle $40^o$ to the vertical. At what angle to the horizontal should a plane mirror be placed?

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. $65^o$

  2. $70^o$

  3. $75^o$

  4. $80^o$

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Correct Option: B
Explanation:

$\begin{array}{l} i+r=i+i=140 \ or\, \, i={ 70^{ 0 } } \end{array}$

Thus, plane mirror makes an angle of $20^0$ with  vertical and $70^0$  with horizontal.
Therefore  , the correct answer is option $C$.

An invisible energy which  causes in us the sensation vision, is

evs light, shadows and images what makes things visible nature and sources of light light travels in straight line

  1. electrical

  2. sound

  3. light

  4. mechanical

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Correct Option: C