Suppose a sound wave and an electromagnetic wave have the same frequency. Which has the longer wavelength?

Solution 8E The mathematical relation between a wave’s wavelength, speed and frequency are given asWavelength = speed/frequency …..(1) Both the waves are given to have the same frequency. Therefore, the only factor that will decide the value of wavelength is the speed. An electromagnetic (EM) wave can travel at the speed of light in vacuum which is 3 × 10 m/s. It varies from medium to medium depending on the medium’s refractive index. Still, the speed value of EM waves remains quite large (~10 m/s). On the other hand, the speed of sound in air is 343 m/s, which is much smaller than 10 m/s. Therefore, from equation (1), the electromagnetic wave will have a longer wavelength.