Question

Find the frequency in terahertz of visible light with a wavelength of 639 nm in vacuum.

Answer 1

The relationship between frequency and wavelength for electromagnetic waves is

`f= (c)/(\lambda)`
where
f is the frequency
c is the speed of light

`\lambda` is the wavelength

For the light in our problem, the wavelength is

`\lambda=639 nm= 6.39 \cdot 10^(-7) m`

and with the previous equation we can find the corresponding frequency:

`f= (c)/(\lambda)= (3 \cdot 10^8 m/s)/(6.39 \cdot 10^(-7) m)=4.69 \cdot 10^(14)Hz`
And since
`1 THz = 10^(12) Hz`, the frequency can be rewritten as

`f=4.69 \cdot 10^2 THz`