Tag: nature and sources of light

Questions Related to nature and sources of light

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.

What is the wavelength range of visible light?

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

  1. $ 4 \times 10^{-7} m $ to $ 8 \times 10^{-7} m$

  2. $ 4 \times 10^{-9} m $ to $ 8 \times 10^{-9} m$

  3. $ 4 \times 10^{-5} m $ to $ 8 \times 10^{-5} m$

  4. $ 4 \times 10^{-6} m $ to $ 8 \times 10^{-6} m$

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Correct Option: A
Explanation:

The wavelength of visible light lies between $400\,{\rm{nm}}$ to $800\,{\rm{nm}}$.

Or, $4 \times {10^{ - 7}}$ to $8 \times {10^{ - 7}}\,{\rm{m}}$

 

In a YDSE with two identical slits, when the upper slit is covered with a thin, perfectly transparent sheet of mica, the intensity at the centre of screen reduces to $75\%$ of the initial value. Second minima is observed to be above this point and third maxima below it. Which of the following can be a possible value of phase difference caused by the mica sheet.

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

  1. $\dfrac{\pi}{3}$

  2. $\dfrac{13\pi}{3}$

  3. $\dfrac{17\pi}{3}$

  4. $\dfrac{11\pi}{3}$

Show answer
Correct Option: D
Explanation:

Here when second order minica replaces bright spot change in path difference$3\pi $


Second order minica phase difference$\dfrac { \pi  }{ 2 } $

Phase difference lies between $3\pi\ to\ 4\pi $ i.e. $\dfrac{11\pi}{3}$