A lens is placed between a source of light and a wall. It forms images of area \[{{A}_{1}}\] and \[{{A}_{2}}\] on the wall for its two different positions. The area of the source or light is [CBSE PMT 1995]

\[{{\left[ \frac{\sqrt{{{A}_{1}}}+\sqrt{{{A}_{2}}}}{2} \right]}^{2}}\]

\[\frac{{{A}_{1}}+{{A}_{2}}}{2}\]

\[{{\left[ \frac{1}{{{A}_{1}}}+\frac{1}{{{A}_{2}}} \right]}^{-1}}\]

A lens is placed between a source of light and a wall. It forms images

1.	A lens is placed between a source of light and a wall. It forms images of area \[{{A}_{1}}\] and \[{{A}_{2}}\] on the wall for its two different positions. The area of the source or light is [CBSE PMT 1995]
A.	\[\frac{{{A}_{1}}+{{A}_{2}}}{2}\]
B.	\[{{\left[ \frac{1}{{{A}_{1}}}+\frac{1}{{{A}_{2}}} \right]}^{-1}}\]
C.	\[\sqrt{{{A}_{1}}{{A}_{2}}}\]
D.	\[{{\left[ \frac{\sqrt{{{A}_{1}}}+\sqrt{{{A}_{2}}}}{2} \right]}^{2}}\]
Answer» D. \[{{\left[ \frac{\sqrt{{{A}_{1}}}+\sqrt{{{A}_{2}}}}{2} \right]}^{2}}\]