λ = 2 m.
The easiest way to solve this problem is using the equation of frecuency of a wave f = v/λ, where v is the velocity of the wave, and λ is the wavelength.
To calculate the wavelength of a microwave light travels through a liquid, it moves at a speed of 2.2 x 10⁸ m/s. If the frecuency of the light wave is 1.1 x 10⁸ Hz, we have to clear λ from the equation f = v/λ:
f = v/λ -------> λ = v/f
λ = 2.2 x 10⁸ m/s / 1.1 x 10⁸ Hz
λ = 2 m (wavelength of the microwave)