Optics Question 80
Question: A square of side $ 3cm $ is placed at a distance of $ 25cm $ from a concave mirror of focal length $ 10cm. $ The centre of the square is at the axis of the mirror and the plane is normal to the axis. The area enclosed by the image of the square is
Options:
A) $ 4cm^{2} $
B) $ 6cm^{2} $
C) $ 16cm^{2} $
D) $ 36cm^{2} $
Show Answer
Answer:
Correct Answer: A
Solution:
$ m=\frac{I}{O}=\frac{f}{u-f}=\frac{10}{25-10}=\frac{10}{15}=\frac{2}{3} $
$ m^{2}=\frac{A _{i}}{A _{o}}\Rightarrow A _{i}=m^{2}\times A _{o} $
$ ={{( \frac{2}{3} )}^{2}}\times {{(3)}^{2}}=4cm^{2} $
