Tag: light, shadows and images

Questions Related to light, shadows and images

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

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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

The illumination on the screen, in case of a movie hall if the distance between the projector and the screen is increased by $1\%$ will be:

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

  1. increased by $1\%$

  2. decreased by $1\%$

  3. increased by $2\%$

  4. decreased by $2\%$

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Correct Option: D
Explanation:

Projector act as a point source

Hence   $E\propto \dfrac{1}{r^{2}}$
$\dfrac{dE}{E}=2\left(\dfrac{\Delta r}{r}\right)=2\times 1\%=2\%$
As the distance increases, the illumination will decrease.

Pick the only wrong statement in the following :

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

  1. Light travels with a speed greater than that of sound

  2. Light cannot travel through vacuum

  3. Light travels in a straight line

  4. Light is a wave motion

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Correct Option: B
Explanation:

Light travels through vacuum for sure as it does not need a material medium for its propagation. Sunlight is the biggest example for this.

Moreover, light has maximum speed in vacuum ,that is, $3\times 10^8$.

A broader bundle of light rays is called a -

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

  1. Beam of light

  2. Ray of light

  3. Bundle of light

  4. None of these

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Correct Option: A
Explanation:

A single wave of light is called a ray.

Bundle of light rays is called beam of light.