Question

A converging lens of focal length 20cm is placed in contact with a diverging lens of focal length 30cm

Answer 1

Answer:

Correct option is

C

15cm

Given, 

Focal length of converging lens, f1=20 cm

Focal length of diverging lens,f2=−5 cm

feq=f1+f2−df1f2

Since there is no deviation, 

feq=∞

⇒f1+f2−d=0

⇒f1+f2=d

20−5=d

⇒d=15 cm