What is the frequency of a microwave with a wavelength of 3.52 mm?

As per the question the wavelength of the microwave is given as 3.52 mm.

we are asked to calculate the frequency of the wave.

we know that microwave is a electromagnetic wave.

As per Clark Maxwell's electromagnetic theory ,every electromagnetic wave moves with a velocity equal to the velocity of light in vacuum and that is equal to 3×10^8 m/s.

From the equation of the wave,we know that velocity of wave is the product of frequency and wavelength.

Mathematically   wave velocity   where f is the frequency of the wave and is the wavelength.

As per the question

                       Here  

Hence frequency of the wave

Here Hertz [Hz] is the unit of frequency.                      

vapour or gas assuming atmospheriv pressure

there are no contact forces mentioned on the list of choices that you've provided.