Question

A beam of light has a wavelength of 4.5 x 10−7 meter in a vacuum. The frequency of this light is ___? (Speed of light is 3 X 108 m/s)

Answer 1

`6.67 * 10^14 Hz`

Explanation:

wave equation:

`s = flambda`

speed = wavelength * frequency

where

`s` is in metres per second `m//s`

`f` is in hertz `Hz`

and `lambda` is in metres `m`.

`s = flambda` can be rearranged as `f = s/lambda`

here, `s = 3 * 10^8 m//s`

and `lambda = 4.5 * 10^-7 m`

`s/lambda = (3 * 10^8)/(4.5 * 10^-7)`

`3/4.5 = 2/3 ~~ 0.667`

`10^8 / 10^-7 = 10^(8 - -7) = 10^(8+7)`

`= 10^15`

`0.667 * 10^15 = 6.67 * 10^14`

`f = 6.67 * 10^14 Hz`