Ray Optics and Optical Instruments - Result Question 47
49. 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 of light is
[1995]
(a) $\sqrt{A_1 A_2}$
(b) $\frac{A_1+A_2}{2}$
(c) $\frac{A_1-A_2}{2}$
(d) $\frac{1}{A_1}+\frac{1}{A_2}$
Show Answer
Answer:
Correct Answer: 49. (a)
Solution:
- (a) Size of images $=A_1$ and $A_2$. From the displacement method, the area of the source of light $=\sqrt{A_1 A_2}$.
