Red light has wavelength 750 nm , whereas violet light has wavele… - Vidyadip

Question

Red light has wavelength 750 nm , whereas violet light has wavelength 400 nm . Calculate their frequency and energy,
$\left(\mathrm{c}=3 \times 10^8 \mathrm{~ms}-1, \mathrm{~h}=6.63 \times 10^{-34} \mathrm{Js}\right)$.

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Answer

$'\lambda_1'=750\text{nm}=750\times10^{-9}\text{m}$
$'\text{C}_1'=3\times10^8\text{ms}^{-1}$
Frequency, $\text{v}=\frac{\text{c}}{\lambda}=\frac{3\times10^8\text{ms}^{-1}}{750\times10^{-9}\text{m}}=4\times10^{14}\text{Hz};$
Energy, $\text{E}=\text{hv}=6.63\times10^{-34}\times4\times10^{14}$
$=2.652\times10^{-19}\text{J}$
$'\lambda'_1=400\text{nm}=400\times10^{-9}\text{m}$
$'\text{c}_2'=3\times10^8\text{ms}^{-1}$
Frequency, $\text{v}=\frac{3\times10^8\text{ms}^{-1}}{400\times10^{-9}\text{m}}=7.5\times10^{14}\text{Hz};$
Energy, $\text{E}=6.63\times10^{-34}\times7.5\times10^{14}$
$=4.972\times10^{-19}\text{J}$

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