µ
1
sin θ
i
= µ
2
+ sin θ
r
---------------- (1)
Where
µ
1
is the refractive index of medium 1 (here air = 1);
θ
i
is the angle of incidence = 30
o
;
µ
2
is the refractive index of medium 2 = 1.5;
θ
r
is the angle of refraction = θ
2
;
Putting these values in equation 1 we get
Or, 1 * sin 30
o
= 1.5 * sin θ
r
Or, 1/2 = 1.5 * sin θ
r
Or, 1/(2*1.5) = sin θ
r
Or, 1/3 = sin θ
r
Or, θ
r
= sin
-1
(1/3)
As θ
r
is same as θ
2
. The angle of refraction is sin
-1
(1/3).
Hence, E is the correct answer option.
Question 15
Which of the following gets deflected by electric field?
A. Gamma rays
B. Infrared rays
C. Beta rays
D. Neutrons
E. X-ray
Correct Answer: C
Explanation:
Electric field can be negative or positive in nature. If the electric field is created by negative charges
then the electric field is negative and if the electric field is created by positive charges then the electric
field is positive. Depending on the type of the charged particle passing through the region of electric
field, deflection can be either attractive or repulsive. Since gamma rays have no charge they will move
further into the electric field without being deflected. Hence, A is an incorrect option. Infrared rays
consist of uncharged particles and therefore, there would not be any deflection from the normal path.
Thus, B is an incorrect option. Beta rays are equivalent to electrons i.e. beta rays have the same
charge as that on electron. Hence, when beta rays pass through an electric field they will either get
attracted or repelled depending on the nature of the electric field. Thus, C is the correct answer
option. Neutrons are neutral like gamma rays or infrared rays. Hence, they will not show any
deflection while passing through the electric field. Therefore, D is an incorrect option. X-rays consists
of neutral particles. Due to this, when they pass through a region of electric field, they undergo no
deflection. Thus, E is an incorrect option as well.