JEE Main202225 Jul 2022Evening ShiftPhysicsRay OpticsActual
For an object placed at a distance 2 . 4 m from a lens, a sharp focused image is observed on a screen placed at a distance 12 cm from the lens. A glass plate of refractive index 1 . 5 and thickness 1 cm is introduced between lens and screen such that the glass plate plane faces parallel to the screen. By what distance should the object be shifted so that a sharp focused image is observed again on the screen?
Options
- A0 . 8   m
- B3 . 2   m
- C1 . 2   m
- D5 . 6   m
Correct answer
B. 3 . 2   m
Step-by-step solution
Given: object using the lens formula: ( aligned & 1 f = 1 v - 1 w^ & 21 240 ~cm = 3 35 ~cm - 1 u^ 1 u^ & = 3 35 ~cm - 21 240 ~cm & 1 u^ = 1 5 [ 3 7 ~cm - 21 48 ~cm ] 1 u^ & = 1 5 [ 144-147 336 ] u^ & =-560 ~cm =-5.6 ~m aligned ) Hence, the object should be at (5.6 ~m ) in front of the lens. Hence, the oblect should be moved by 5.6-24= (3.2 ~cm ).