Tag: polarisation

Questions Related to polarisation

The angle of incidence at which reflected light is totally polarised for reflection from air to glass (refractive index n) is :

polarisation of light polarisation wave optics optics physics

  1. $sin^{-1}(n)$

  2. $sin^{-1}(1/n)$

  3. $ tan^{-1}(n)$

  4. $ tan^{-1}(1/n)$

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Correct Option: C
Explanation:

The refractive index of glass is n
If the light is incident on the surface with an angle of incidence i given by tan i $=\mu $ using the Brewster's law the reflected light is completely polarized.
Here tan i $=n$
i$=tan^{-1}(n)$

A light ray is incident on a transparent medium of $\mu =$ 1.732 at the polarizing angle. The angle of refraction is :

polarisation of light polarisation wave optics optics physics

  1. 60$^{\circ}$

  2. 30$^{\circ}$

  3. 45$^{\circ}$

  4. 90$^{\circ}$

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Correct Option: B
Explanation:

Angle of incidence $=$ polarising angle
$tan i = \mu $
$tan i = 1.732$
$i = 60^{0}$
From snell's law
$\dfrac{sin i}{sin \gamma }=\mu $
$sin \gamma =\dfrac{sin 60^{0}}{1.732}$
$\gamma =30^{0}$

The critical angle for total internal reflection for a substance is $45^{\circ}$. The polarizing angle for this substance is ($\tan 54^{\circ}44'=\sqrt{2}$) :

polarisation of light polarisation wave optics optics physics

  1. $46^{\circ}16'$

  2. $54^{\circ}44'$

  3. $46^{\circ}44'$

  4. $54^{\circ}16'$

Show answer
Correct Option: B
Explanation:

If polarizing angle is $\theta $
Then tan $\theta =\dfrac{1}{sin c}$
$tan \theta =\dfrac{1}{sin 45}=\sqrt{2}$
$\theta =54^{0}{44}'$

ASSERTION (A):Hyugens' theory failed to explain polarization
REASON (R): According to Hyugens' theory light is longitudinal wave

polarisation of light polarisation wave optics optics physics

  1. A is correct, R is correct and it is the correct explanation

  2. A is correct, R is correct but it is not a correct explanation

  3. A is correct, R is wrong

  4. A is wrong , R is correct

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Correct Option: A
Explanation:

Huygen's theory failed to explain polarisation because according to the Huygen's theory light is a longitudinal waves and longitudinal wave does not shows polarisation.

According to Maxwell , most of the optical properties of light depend on

polarisation of light polarisation wave optics optics physics

  1. Magnetic vector

  2. Electric vector

  3. Both Electric and Magnetic vectors

  4. Can not be decided

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Correct Option: B
Explanation:

The experiments on stationary light waves establish that most of the optical properties of light depends on the electric vector, which is also known as light vector.

Identify which of the following should be used for polarised light waves?
I. Sunglasses
II. Remove ultraviolet light
III. Reveal stress patterns

polarisation of light polarisation wave optics optics physics

  1. I only

  2. II only

  3. I and III only

  4. II and III only

  5. I, II, and III

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Correct Option: C
Explanation:

Polarizers are used in industry to reveal stress patterns in machinery and tools. Sunglasses are used to protect the eyes by polarizing the light to reduce glare using the tailor-made material of the glasses.

Three waves are given below.
I. Sound waves
II. Visible light waves
III. X-rays

Which of the above waves cannot be polarised?
polarisation of light polarisation wave optics optics physics

  1. I only

  2. III only

  3. I and II only

  4. I and III only

  5. I, II and III

Show answer
Correct Option: A
Explanation:

Only the transverse waves can be polarized.

As the sound waves are longitudinal waves in nature whereas visible light rays and X-rays are transverse waves.
Thus sound waves cannot be polarized.

Light waves exhibit polarization but sound waves do not exhibit polarization because they are not:

polarisation of light polarisation wave optics optics physics

  1. longitudinal

  2. coherent

  3. dispersive

  4. transverse

  5. refractive

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Correct Option: D
Explanation:

Only transverse waves can exhibit polarization.
Light waves are transverse waves whereas sound waves are longitudinal waves, hence sound waves can not be polarized.

Making a light wave vibrate in only one plane is known as :

polarisation of light polarisation wave optics optics physics

  1. refraction.

  2. reflection

  3. Interference

  4. diffraction

  5. polarization.

Show answer
Correct Option: E
Explanation:

Light in the form of a plane wave in space is said to be linearly polarized. Light is a transverse electromagnetic wave, but natural light is generally unpolarized, all planes of propagation being equally probable. 

The process of making the light wave vibrated in a single plane is known as polarization.

Why do polarized sun glasses block out some reflected light (glare), but do not block out light that has not been reflected?

polarisation of light polarisation wave optics optics physics

  1. Some reflected light is at least partially polarized

  2. Some reflected light changes frequency

  3. Some reflected light is red-shifted

  4. Some reflected light is at least partially diffracted

  5. Some reflected light splits into multiple photons

Show answer
Correct Option: A
Explanation:

When ordinary (unpolarised) light is reflected from a surface , it gets partial polarisation , it means some of the electric vectors in some planes are cut-off . When this partially polarized light is incident on polarized glasses , glass acts as an analyser and therefore block out some reflected light .