Spherical mirrors MCQs

Q1. A convex mirror used as a rear-view mirror in a car has a radius of curvature of 3.0 m. A car 5 m behind it appears at what distance behind the mirror?

• A.approximately 1.15 m
• B.approximately 5 m
• C.approximately 0.6 m
• D.approximately 3 m

Answer: A. approximately 1.15 m

Given 3.0 m, 5 m, asked for the unknown. By Convex mirror: f = +R/2 = +1.5 m. Convex mirror: f = +R/2 = +1.5 m → u = -5 m → 1/v = 1/f - 1/u = 1/1.5 + 1/5 = 0.667 + 0.2 = 0.867, v = 1/0.867 ≈ 1.15 m (positive, behind mirror) → Trap 0.6 m comes from 1/v = 1/1.5 - 1/5 = 0.667 - 0.2 = 0.467 with wrong sign handling. Putting it together option A) approximately 1.15 m.

Q2. A concave makeup mirror is ground to a radius of curvature of 24 cm. Given R = 2f, what is its focal length?

• A.24 cm
• B.12 cm
• C.6 cm
• D.48 cm

Answer: B. 12 cm

For a spherical mirror f = R/2 = 24/2 = 12 cm.

Q3. The reflecting bowl of a solar cooker forms a concave mirror with radius of curvature 36 cm. Since the focus lies halfway to the centre of curvature, what is its focal length?

• A.9 cm
• B.72 cm
• C.18 cm
• D.36 cm

Answer: C. 18 cm

For a spherical mirror f = R/2 = 36/2 = 18 cm.