An electromagnetic wave of frequency 3GHz enters a dielectric...

$\lambda$ in vacuum $= \dfrac{c}{f} = \dfrac{3 \times {10}^{8}}{3 \times {10}^{9}} = 0 . 1m$

$∴ \lambda$ in medium $= \dfrac{0 . 1}{\mu}$

Where refractive index

$\mu = \sqrt{{\mu}_{r}{ε}_{r}}$

Assuming non-magnetic material ${\mu}_{r} = 1$

$∴ \mu = \sqrt{2 . 25} = 1 . 5$

${\lambda}_{m} = \dfrac{0 . 1}{1 . 5} = \dfrac{1}{15}m = 6 . 67cm$

$= 667 \times {10}^{- 2}cm$