Question

Calculate the frequency of radiation of each of the
following wavelengths: (a) 8973Å, (b) 442 nm, (c) 4.92 cm,
(d) 4.55 3 1029 cm.

Answer 1

Think back, what is the formula for speed?

distance=rate*time

So if we talk about light, we know it has a constant speed, the speed of light! Little algebra:

Speed of light = distance/time

Now, what is a wavelength? The distance you go in one oscillation. What is the period of a motion? It's the amount of time it takes to make one oscillation.

So if we see that light travels the distance of its wavelength in one period, we can say:

Speed of light = wavelength/period

What is frequency? The number of oscillations in an amount of time, usually counted in seconds. This is the inverse of the period. frequency = 1/period.

Therefore,

speed of light = wavelength*frequency

Now if you know the frequency or wavelength of any particle, you can always just plug it in and divide it from the speed of light to find the other. Easy peasy.