Question

A cube of side 2 m is placed in front of a concave mirror focal length 1m with its face P at a distance of 3m and face Q at a distance of 5 m from the mirror. The distance between the images of face P and Q and height of images of P and Q are

(a)  1 m, 0.5 m, 0.25 m

(b)  0.5 m, 1 m, 0.25 m

(c)  0.5 m, 0.25 m, 1 m

(d)  0.25 m, 1 m, 0.5 m

Answer 1

Correct option (d) 0.25 m, 1 m, 0.5 m

Explanation :

For point ‘P ’ 1/V_p - 1/3 = -1/1 ⇒ 1/V_p = -1 + 1/3

V_p =  - 3/2 m

For point ‘Q ’  1/V_p - 1/5 = -1/1 ⇒1/V_q = -1 + 1/5

V_{q =} -5/4

So V_p - ­ V_Q = 0.25m

Height of image of ‘P ’ ⇒ m = -v/u = h₁/h₀

= - (+3/2/+ 3) = h₁/2m ⇒ h_{1 =} - 1/2m

Height of image ‘Q’  ⇒ m = -(-5/4/5) 

 = h₁/2m

h₁ = 0.25m

So height of image of Q pace = 0.5m

Height of image of P pace = 1.0m