Tag: polarisation

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Questions Related to polarisation

Multiple choice polarisation of light polarisation wave optics optics physics

The angle of incidence of light is equal to Brewster's angle, then 
A) Reflected ray is perpendicular to refracted ray
B) Reflected ray is parallel to refracted ray
C) Reflected light is polarized having its electric vector in the plane of incidence 
D) Refracted light is polarized.

  1. (A) and (D) are true

  2. (A) and (B) are true

  3. (A) and (C) are true

  4. (B) and (C) are true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At Brewster's angle, the reflected and refracted rays are perpendicular (A). The reflected light is polarized perpendicular to the plane of incidence (C is incorrect). The refracted light is partially polarized (D is correct).

Multiple choice polarisation of light polarisation wave optics optics physics

A beam of unpolarised light of intensity $I _{0}$ is passed through a polaroid $A$ and then through another polaroid $B$ which is oriented so that its principal plane makes an angle of $45^{\circ}$ relative to that of $A$. The intensity of the emergent light is

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

When unpolarized light of intensity I0 passes through the first polaroid A, its intensity becomes I1 = I0 / 2. When it passes through the second polaroid B at an angle of 45 degrees, Malus's law applies: I2 = I1 * cos^2(45) = (I0 / 2) * (1 / 2) = I0 / 4.

Multiple choice polarisation of light polarisation wave optics optics physics

Polarizing angle for water is $53^o4'$. If light is incident at this angle on the surface of water and reflected the angle of refraction is:

  1. $53^o4'$
  2. $126^o56'$
  3. $36^o56'$
  4. $30^o4'$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At the polarizing angle, i_p + r = 90 degrees. r = 90 - 53 degrees 4 minutes = 36 degrees 56 minutes.

Multiple choice polarisation of light polarisation wave optics optics physics

Through which character we can distnguish the light waves from sound waves.

  1. Interference

  2. Refraction

  3. Polarisation

  4. Reflection
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both light and sound waves exhibit interference, refraction, and reflection because these are general wave properties. However, light is a transverse electromagnetic wave and can be polarized, whereas sound is a longitudinal pressure wave and cannot be polarized.

Multiple choice polarisation of light polarisation wave optics optics physics

In the propagation of light waves, the angle between the direction of vibration and plane of polarization is :

  1. $0^{ \circ }$
  2. $90^{ \circ }$
  3. $45^{ \circ }$
  4. $80^{ \circ }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In transverse wave propagation, the direction of vibration of the electric field vector is perpendicular to the direction of wave travel, while the plane of polarization contains the direction of propagation and the vibration vector. Thus, the angle between the direction of vibration and the plane of polarization is 90 degrees.

Multiple choice polarisation of light polarisation wave optics optics physics

A stretched string is 1 m long. Its mass per unit length is 0.5 g/m. It is stretched with a force of 20 N. It plucked at a distance of 25 cm from one end. The frequency of note emitted by it will be:

  1. $400 Hz$
  2. $300 Hz$
  3. $200 Hz$
  4. $100 Hz$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice polarisation of light polarisation wave optics optics physics

Which of the following cannot be polarised

  1. Radio waves

  2. UV rays

  3. IR rays

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

Polarization is a property of transverse waves. Ultrasonic waves are longitudinal waves and cannot be polarized.

Multiple choice polarisation of light polarisation wave optics optics physics

A beam of light strikes a piece of glass at an angle of incidence of $60 ^ { \circ }$ and the reflected beam is completely Plane polarised. Find the refractive index of this glass

  1. $\sqrt { 2 }$
  2. $\sqrt { 3 / 2 }$
  3. $\sqrt { 3 }$
  4. $\cfrac { 3 } { 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Refractive index mu = tan(i_p) = tan(60) = sqrt(3).

Multiple choice polarisation of light polarisation wave optics optics physics

If the polarizing angle for a given medium is $60^{\circ}$, then the refractive index of the medium is 

  1. $\dfrac{1}{\sqrt 3}$
  2. $\sqrt{\dfrac{3}{2}}$

  3. 2
  4. $\sqrt{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Refractive index mu = tan(i_p) = tan(60) = sqrt(3).

Multiple choice polarisation of light polarisation wave optics optics physics

A polarizer and an analyzer are arranged with their optic axes parallel to each other Symmetric light first passes through the polarizer and then the analyzer and the intensity of the light emerging is 'I'. If the analyzer is turned through $30^o$, the percent changes in the intensity is

  1. $75\%$
  2. $50\%$
  3. $25\%$
  4. $40\%$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial intensity I = I_0. After turning 30 degrees, I' = I_0 * cos^2(30) = I_0 * 3/4. The change is I_0 - 0.75I_0 = 0.25I_0, which is 25%.