Optics Question 799
Question: A hemispherical glass body of radius 10 cm and refractive index 1.5 is silvered on its curved surface. A small air bubble is 6 cm below the flat surface inside it along the axis. The position of the image of the air bubble made by the mirror is seen:
Options:
A) 14 cm below flat surface
B) 20 cm below flat surface
C) 16 cm below flat surface
D) 30 cm below flat surface
Show Answer
Answer:
Correct Answer: B
Solution:
[b] Given, radius of hemispherical glass R=10cm
$ \therefore $ Focal length $ f=\frac{10}{2}=-5cm $
$ u=( 10-6 )=-4cm. $
By using mirror formula, $ \frac{1}{v}+\frac{1}{u}=\frac{1}{f}\Rightarrow \frac{1}{v}+\frac{1}{-4}=\frac{1}{-5}\Rightarrow v=20cm. $
Apparent height, $ h _{a}=h _{r}\frac{{\mu _{1}}}{{\mu _{2}}}=30\times \frac{1}{1.5}=20cm $ below flat surface.
