Tag: light travels in straight line

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Questions Related to light travels in straight line

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

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?

  1. $65^o$
  2. $70^o$
  3. $75^o$
  4. $80^o$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $C$.

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

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:

  1. increased by $1\%$
  2. decreased by $1\%$
  3. increased by $2\%$
  4. decreased by $2\%$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Pick the only wrong statement in the following :

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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, $3\times 10^8$.

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

What is the wavelength range of visible light?

  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$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

 

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

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.

  1. $\dfrac{\pi}{3}$
  2. $\dfrac{13\pi}{3}$
  3. $\dfrac{17\pi}{3}$
  4. $\dfrac{11\pi}{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
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. $\dfrac{11\pi}{3}$