question_answer

A convex lens is put 10 cm from a light source and it makes a sharp image on a screen, kept 10 cm from the lens. Now a glass block (refractive index 1.5) of 1.5 cm thickness is placed in contact with the light source. To get the sharp image again, the screen is shifted by a distance d. Then d is: [JEE Main 09-Jan-2019 Morning]

A)             0.55 cm towards the lens

B)             0

C)             0.55 cm away from the lens

D)             1.1 cm away from the lens

Correct Answer: C

Solution :

[c]

Shift due to slab =

Now for lens

So, screen is shifted away from lens by 0.55 cm.