Question

M₁ and M₂ are two concave mirrors of the same focal length 10 cm. AB & CD are their principal axis respectively. A point object O is kept on the line AB at distance 15 cm from M₁. The distance between the mirrors is 20 cm. Considering two successive reflections first on M₁ and then on M₂. The distance of final image from the line AB is –

• A. 3 cm
• B. 1.5 cm
• C. 4.5 cm
• D. 1 cm

Answer 1

Answer: (B)

1.5 cm

Answer 2

Ist reflection on M₁

$\frac { 1 } { v } + \frac { 1 } { u } = \frac { 1 } { \mathrm { f } }$ Ž Ž $\frac { 1 } { v } = \frac { 1 } { 15 } - \frac { 1 } { 10 }$

v = – 30 cm

2^nd Reflection on M₂ , Ž

v = – 5, m = – , m = $+ \frac { 1 } { 2 }$

Distance = $\frac { 1 } { 2 }$ × 3 = 1.5 cm