What is an example of an electromagnetic radiation practice problem?

1 Answer
Apr 25, 2015

Background: Electromagnetic radiation moves at the speed of light in a vacuum. The speed of light, c, to three significant figures, is 3.00xx10^8"m/s". The relationship between wavelength, lambda, and frequency, f, is c=lambda*f.

Question: If the wavelength of a photon of red light is 725"nm", what is its frequency?

Answer:
Convert 725"nm" to meters. (1"m"=1xx10^9"nm")
725 cancel"nm"xx(1 "m")/(1xx10^9 cancel"nm")=7.25xx10^(-7) "m"

Rearrange c=lambda*f to solve for f.

f=c/lambda = (3.00xx10^8 cancel("m")/s")/(7.25xx10^(-7) cancel(m)= 4.14xx10^14 "/s"=4.14xx10^14 "Hz"