JEE Main 2022 · 25 Jul · Shift 2 · Physics Q38

← JEE Main 2022 · 25 Jul · Shift 2

PhysicsSingle correct+4 / -1Question 38 of 90

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 form 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 screeen ?

0.8 m

3.2 m

1.2 m

5.6 m

Answer and worked solution

Official answer: B

Lens. $\frac1f=\frac1{12}+\frac1{240}$ . The plate shifts the image $1\left(1-\frac1{1.5}\right)=\frac13$ cm, so the lens must now form it at $\frac{35}3$ cm.

New object distance $\dfrac1u=\dfrac{21}{240}-\dfrac3{35}$ , $u=560$ cm: shift $3.2$ m.

(B)

Topics:Thin lenses and lens maker's formula Refraction at plane surfaces

← Previous question Next question →

JEE Main 2022 · 25 Jul · Shift 2, Physics question 38