Tag: physics

Questions Related to physics

A ray of unplorised incident on a glass plate at the polarising angle $57^{o}$. Then

  1. The reflected ray and the transmitted ray both will be completely polarised

  2. The reflected ray will be completely polarised and the transmitted ray will be partially polarised

  3. The reflected ray will be partialy polarised and the transmitted ray will be completely polarised

  4. The replected and transmitted both ray will be partially polarized


Correct Option: A

The critical angle for a medium is $ 45^o $ What is polarising angle? Angle refraction ?

  1. $ 34.7^o, 32.3^o $

  2. $ 64.7^o, 30.3^o $

  3. $ 54.7^o, 35.3^o $

  4. $ 44.7^o, 45.3^o $


Correct Option: C

When sun light is incident on water at an angle of $ 53^o $ the reflected light is found to be completely plane-polarised. Determine : (i) angle of refraction of light,
(ii) refractive index of water.

  1. (i) $ 31^o $
    (ii) $ 1.427 $

  2. (i) $ 30^o $
    (ii) $ 2.327 $

  3. (i) $ 27^o $
    (ii) $ 1.327 $

  4. (i) $ 37^o $
    (ii) $ 1.327 $


Correct Option: D

The angle between polariser and analyser is $30 ^ { \circ }$  The ratio of intensity of incident light and transmitted by the analyser is

  1. 3:4

  2. 4:3

  3. $\sqrt { 3 } : 2$

  4. $2 : \sqrt { 3 }$


Correct Option: A
Explanation:
Given,
$\theta=30^0$
By using malus law,
$I=I _0cos^2\theta$
$\dfrac{I}{I _0}=(cos30)^2$
$\dfrac{I}{I _0}=(\dfrac{\sqrt{3}}{2})^2=\dfrac{3}{4}$
ratio, $I:I _0=3:4$
The correct option is A.

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


Correct Option: A

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. $I _{0}/8$


Correct Option: A

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. $30^o4'$


Correct Option: C

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

  1. Interference

  2. Refraction

  3. Polarisation

  4. Reflection


Correct Option: A

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. $80^{ \circ }$


Correct Option: C

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. $100 Hz$


Correct Option: C