Q 12-08-157JEE MainJEE Main 2021 (24 Feb, Shift 2)Easy
An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2.25 from vacuum. The wavelength of this wave in that medium will be ______ $\times10^{-2}$ cm.
Numerical value type. Enter your answer.
Answer: 667
In vacuum $\lambda_0 = \dfrac{3\times10^8}{3\times10^9} = 0.1$ m $= 10$ cm. The refractive index is $n = \sqrt{2.25} = 1.5$.
$$\lambda = \frac{\lambda_0}{n} = \frac{10}{1.5} = 6.67\ \text{cm} = 667\times10^{-2}\ \text{cm}$$
Solution by Sreeraj P, M.Sc Physics