Question

An object is located in a fixed position in front of a screen. Sharp image is obtained on the screen for two positions of a thin lens separated by $10\, cm$. The size of the images in two situations are in the ratio 3 : 2. What is the distance between the screen and the object ?

• A. $124.5 \,cm$
• B. $144.5 \,cm$
• C. $65.0 \,cm$
• D. $99.0\, cm$

Answer 1

Answer: (D)

$\frac{m_{1}}{m_{2}} = \frac{3}{2} = \left(\frac{D+10}{D-10}\right)^{2}$
$D = 99\,cm$