2019-03-01_Physics_Times

30.

Two polaroids are placed in the path of unpolarised

beam of intensity I 0 such that no light is emitted

from the second polaroid. If a third polaroid whose

polarisation axis makes an angle  with the

polarisation axis of first polaroid, is placed between

these polaroids then the intensity of light emerging

from the last polaroid will be

(a) I cos 0 4  (b)

(^022)
8
I
sin 
 
 
 
(c)
0 4
2
I
sin
 
 
 
(d)
(^022)
4
I
sin 
 
 
 
The Fraunhofer diffraction pattern of a single slit
is formed in the focal plane of a lens of focal length
1 m. The width of slit is 0.3 mm. If third minimum is
formed at a distance of 5 mm from central maximum,
then wavelength of light will be
(a) 2500 A

(b) 5000 A

(c) 8500 A

(d) 7500 A

A string is hanging from a rigid support. A
transverse wave pulse is generated at its free end.
The speed of wave pulse at distance x from its free
and is proportional to
(a) x^2 (b) x (c) x (d)
1
x
The superposing waves are represented by the
following equations y 1 5sin 2 10 0.1 ,  t x
y 2 10sin 2 10  t 0.1x Ratio of intensities
max
min
I
I will be
(a) 16 (b) 1 (c) 9 (d) 4
The pulley shown in the figure. has a radius r,
moment of inertia I about its axis and mass m. Find
the time period of vertical oscillations of its centre
of mass. the spring constant of spring is K and the
spring does not slip over the pulley.
(a)
m I R/^2
K

 (b)
/^2
2
2
m I R
K


(c)
2 /^2
2
m I R
K

 (d)
/^2
2
m I R
K


The displacement equation of the SHM obtained
by combining the motions x 1 2 sint,
2 4 sin
6
x t


 
   
 
and 3 6 sin
3
x t


 
   
 
is.
(a) x11.10 sin( t 31.54 )
(b) x9.24 sin(  t 37.1 )
(c) x8.20 sin(  t 23.4 )
(d) x12.10 sin(  t 19.1 )
d c d a c
b d a c d

a a a b b

c b c b b

b a a c b

b c c b a

1/ 4 1/ 4

2 1

1 2

4300

4.55

10

A h

A h

   

    

   

0.2

4.55 11.37

0.5

x

   x m

Before connecting E, the circuit diagram is as

shown in the figure.

1.Sol:

2.Sol:

Current in the circuit,

12V 1

I A

24 2

 

