Question

Calculate the frequency in hertz of photons of light with energy of 8.10 × 10-19 J.

Answer 1

The Planck–Einstein relation $E=hv$ gives that E, the photon energy, is equal to h, Planck's constant, times ν, the frequency.

We can solve the equation in terms of frequency to get
$v= \dfrac{E}{h}$

We substitute our given energy, $8.10 \times 10^{-19} J$, and Planck's constant, $6.626 \times 10^{-34} Js$.

$v= \dfrac{8.10 \times 10^{-19} J}{6.626 \times 10^{-34} Js}=1.22 \times 10^{15} s^{-1}=1.22 \times 10^{15} Hz$