Question

M1 and m2 are two plane mirrors which are kept parallel to each other a shown. There is a point o on perpendicular screen just in front of s

Answer 1

Answer:

Explanation:

Correct option is

B

2D

3d  

2

 

​

 

Light emerging from point S gets reflected from mirrors M  

1

​

 and M  

2

​

, to interfere constructively at point O.  

This means that path difference between light travelling SM  

1

​

O and SM  

2

​

O must be λ.  

As shown in the figure, path  SM  

1

​

O=2  

(  

2

D

​

)  

2

+(  

2

d

​

)  

2

 

​

 

path  SM  

2

​

O=2  

(  2 D )  

2 +d  

2

 

​2  

(  2 D )  

2  +d  

2

 

​

  − 2  (  2 D)  

2  +(  2 d  )  

2  =λ

Thus using Bionomial expansion, λ comes out to be  

2D

3d  

2

 

​

.

λ,0)]