Question

Radio waves and microwaves are used in therapy to provide "deep heating" of tissue because the waves penetrate beneath the surface of the body and deposit energy. We define the penetration depth as the depth at which the wave intensity has decreased to 37% of its value at the surface. The penetration depth is 15 cm for27 MHz radio waves. For radio frequencies such as this, the penetration depth is proportional to λ−−√, the square root of the wavelength.

What is the wavelength of 27 MHz radio waves?

Answer 1

Wavelength of \(27 \mathrm{MHz}\) radio waves

We have

$$ \begin{aligned} c &=v \lambda \\ \lambda &=\frac{c}{v} \\ &=\frac{3 \times 10^{8}}{27 \times 10^{5} \mathrm{~Hz}} \\ &=0.111 \times 10^{2} \mathrm{~m} \end{aligned} $$