Question

A microwave oven emits a microwave with a wavelength of 2.00 × 10^−2 meter in air. Calculate the
frequency of the microwave. [Show all work, including the equation and substitution with units.]

Answer 1

Frequency = (speed) / (wavelength)

The speed of microwave is the same as the speed of TV signals,
X-rays, and heat radiation.  We call it the "speed of light".

It's not exactly, but very close to, 3 x 10⁸ m/s, in vacuum or air.

Frequency =

         (3 x 10⁸ meter per sec) / (2.0 x 10⁻² meter) = 

                                                 1.5 x 10¹⁰ per sec = 15 GHz .

Using the information given in the question, this is the answer.
But in the real world, its very inaccurate.

The real wavelength of the radio waves inside the microwave oven is
more like 12 cm, not 2.0 cm.  The ovens operate at 2.56 GHz in the US.