Question

A particle is moving in a circle of radius $1 \, cm$ and with a constant speed of $8 \, cm \, s^{- 1}$ . Centre of the circle lies on principal axis of a converging lens of focal length $50 \, cm$ and at a distance of $75 \, cm$ from the lens. Plane of the circle is perpendicular to principal axis,. The correct statement is

• A. Speed of the image is $4cms^{- 1}$
• B. Speed of the image is $8cms^{- 1}$
• C. Speed of the image is $16cms^{- 1}$
• D. Speed of the image is $3.2cms^{- 1}$

Answer 1

Answer: (C)

$m=\frac{f}{f + u}=-2$
$\Rightarrow $ radius of image = $2cm$
$\because \, \omega $ is same
$\Rightarrow \frac{8}{1}=\frac{v}{2}\Rightarrow v=16 \, cms^{- 1}$ .