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)

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Answer 1 · 2018-03-09T17:58:37

$6.67 * 10^14 Hz$

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 $lambda = 4.5 * 10^-7 m$

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

$3/4.5 = 2/3 ~~ 0.667$

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

$= 10^15$

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

$f = 6.67 * 10^14 Hz$