Optics Question 334
Question: If c is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant K and relative permeability $ {\mu _{r}} $ is
[Kerala PET 2005]
Options:
A) $ v=\frac{1}{\sqrt{{\mu _{r}}K}} $
B) $ v=c\sqrt{{\mu _{r}}K} $
C) $ v=\frac{c}{\sqrt{{\mu _{r}}K}} $
D) $ v=\frac{K}{\sqrt{{\mu _{r}}C}} $
Show Answer
Answer:
Correct Answer: C
Solution:
Speed of light of vacuum $ c=\frac{1}{\sqrt{{\mu _{0}}{\varepsilon _{0}}}} $
and in another medium $ v=\frac{1}{\sqrt{\mu \varepsilon }} $
$ \frac{c}{v}=\sqrt{\frac{\mu \varepsilon }{{\mu _{0}}{\varepsilon _{0}}}}=\sqrt{{\mu _{r}}K} $
Therefore $ v=\frac{c}{\sqrt{{\mu _{r}}K}} $
