Question

A thin rod of length lies along the axis of a concave mirror of focal length f. One end of its magnified image touches an end of the rod, the length of the image is –

• A. f
• B. f/2
• C. 2f
• D. f/4

Answer 1

Answer: (B)

f/2

Answer 2

u₁ = v₁ = 2f – (i)

u₂ = – = –

v₂ = ? f = –f

by mirror formula

$\frac { 1 } { v _ { 2 } }$ = $\frac { 1 } { \mathrm { f } }$ – = + = – $\frac { 2 } { 5 \mathrm { f } }$

v₂ = –

Size of image = |v₂| – |v₁|

= $\frac { 5 f } { 2 }$ – 2f =