Tag: optics

Quizzes (33) Questions (198)

Questions Related to optics

Multiple choice polarisation of light polarisation wave optics optics physics

Light from sodium lamp is made to pass through two polaroids placed one after the other in the path of light. Taking the intensity of the incident light as 100%, the intensity of the out coming light that can be varied in the range: 

  1. 0% to l00%

  2. 0% to 50%

  3. 0% to 25%

  4. 0% to 75%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let $I _0$ be the intensity of incident light. As the light coming from sodium lamp is unpolarised, so the intensity of the light emerging from the first polaroid is
$I _1 \, = \, \dfrac{I _0}{2}$
If $\theta$ is angle between two polaroids, then the intensity of the light emerging from the second polaroid is
$I _2 \, = \, I _1 \, cos^2\theta \, = \, \dfrac{I _0}{2} cos^2\theta$
But $I _0 \, = \, 100%$ (Given)
$\therefore \, I _1\, = \, 50% \, cos^2\theta$
Since $\theta$ varies from 90 to 0, so the intensity of the outcoming light  can be varied from 0% to 50%.

Multiple choice polarisation of light polarisation wave optics optics physics

If the critical angle be $ \theta$ , then the Brewster's angle is

  1. $\sin^{-1}[\cot \theta]$
  2. $90-\theta$
  3. $\tan^{-1}[cosec \theta]$
  4. $\sin^{-1}[\tan \theta]$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Brewster's angle i_p satisfies tan(i_p) = mu, and critical angle theta_c satisfies sin(theta_c) = 1/mu. Thus, tan(i_p) = 1/sin(theta_c) = cosec(theta_c), so i_p = tan^-1(cosec(theta_c)).

Multiple choice polarisation of light polarisation wave optics optics physics

Unpolarised light of intensity $I _{o}$ passes through two polaroids; the axes of one is vertical. The intensity of transmitted light is:

  1. $\dfrac {l _{0}}{4}$
  2. $\dfrac {l _{0}}{8}$
  3. $\dfrac {l _{0}}{2}$
  4. $\dfrac {3l _{0}}{4}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When unpolarized light passes through a polarizer, the intensity becomes I_0/2. The second polarizer's orientation does not change the intensity of the already polarized light if we assume the question implies the first polarizer is the one with the vertical axis.

Multiple choice polarisation of light polarisation wave optics optics physics

The plane of variation and the plane of polarisation of beam of light

  1. are identical to each other

  2. are orthogonal to each other

  3. make an angle. which depends on the colour of the light

  4. rotate with respect to each other along the path of the beam
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By definition, the plane of polarization is the plane containing the direction of propagation and the electric field vector, which is the plane of vibration.

Multiple choice polarisation of light polarisation wave optics optics physics

Choose the correct statement ______

  1. Brewster's angle is independent of the wavelength of light.

  2. Brewster's angle is independent of nature of reflecting the surface.

  3. Brewster's angle is different for different wavelengths.

  4. Brewster's angle depends on the wavelength but not on the nature of reflecting the surface.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Brewester's angle depends on the wavelength of light because Brewester's angle depends on the refractive index of medium and refractive index depends on the wavelength of light. 

Multiple choice polarisation of light polarisation wave optics optics physics

For a given medium, the polarising angle is $  60^{\circ} .  $ What is the critical angle for this medium?

  1. $\tan^{-1}(\dfrac 1{\sqrt 3})$
  2. $\sin^{-1}(\dfrac 1{\sqrt 3})$
  3. $\tan^{-1}( {\sqrt 3})$
  4. $\sin^{-1}({\sqrt 3})$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Refractive index mu = tan(i_p) = tan(60) = sqrt(3). Critical angle theta_c = sin^-1(1/mu) = sin^-1(1/sqrt(3)).

Multiple choice polarisation of light polarisation wave optics optics physics

Which of the following properties shows that light is a transverse wave?

  1. Reflection

  2. Interference

  3. Diffraction

  4. Polarization
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The polarization phenomenon, verifies the transverse nature of light. Since sound has longitudinal nature, so it does not show polarization effect.

Multiple choice polarisation of light polarisation wave optics optics physics

When the light is incident at the polarizing angle on transparent medium, then the completely polarized light is 

  1. refracted light

  2. reflected light

  3. refracted and reflected light

  4. neither reflected nor refracted light
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When the light is incident at the polarising angle on the transparent medium, the reflected light is completely polarised.

Multiple choice polarisation of light polarisation wave optics optics physics

Which of the following cannot be polarised ?

  1. Radio waves
  2. $\beta$ rays

  3. Infrared rays
  4. $\gamma$ rays
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$ \beta $ are stream of particles comprising of electrons moving with very high velocity, hence it cannot be polarized, while others can as they are electromagnetic waves.