# Answer to Question #38953 in Optics for Preet

Question #38953

A small object is placed 20 cm in front of a block of glass 10 cm thick and its farther side silvered.The image is formed 22 cm behind the silvered face.Find refractive index of glass.

options are :

(1) 1.15

(2) 1.25

(3) 1.67

(4) 1.1

options are :

(1) 1.15

(2) 1.25

(3) 1.67

(4) 1.1

Expert's answer

## Comments

Assignment Expert02.07.18, 16:20Dear Muskan, this problem can be solved in a following way. Observer will see the mirror closer due to refraction in glass slab. Let now consider this distance as 20 + x. On the other hand, image distance from the mirror should be the same and we can write as 22 + (10 - x). Now we can find that x = 6, and the real depth of the slab is 10. So we obtain the same answer n=10/6=1.67

Muskan29.06.18, 08:30Why we have add x to the thickness of glass slab and equate it to 22

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