# Problem: It takes 7.21 x 10 -19 J of energy to remove an electron from an iron atom. What is the maximum wavelength of light that can do this?

###### FREE Expert Solution

We are asked to calculate the maximum wavelength of light that takes  takes 7.21 x 10 -19 J of energy to remove an electron from an iron atom

Calculate the wavelength from the total energy (ΔE).

ΔE = 7.21 x 10 -19 J
h = 6.626x10-34 Js

$\overline{){\mathbf{∆}}{\mathbf{E}}{\mathbf{=}}{\mathbf{h}}{\mathbf{\nu }}}$

In the equation, the frequency of the light is used but we need wavelength. We can relate frequency and wavelength using the speed of light:

$\overline{){\mathbf{c}}{\mathbf{=}}{\mathbf{\lambda }}{\mathbf{·}}{\mathbf{\nu }}}\phantom{\rule{0ex}{0ex}}\frac{\mathbf{c}}{\mathbf{\lambda }}\mathbf{=}\frac{\overline{)\mathbf{\lambda }}\mathbf{·}\mathbf{\nu }}{\overline{)\mathbf{\lambda }}}\phantom{\rule{0ex}{0ex}}\overline{){\mathbf{\nu }}{\mathbf{=}}\frac{\mathbf{c}}{\mathbf{\lambda }}}$

c = speed of light = 3.0x108 m/s
▪
λ = wavelength, m

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###### Problem Details

It takes 7.21 x 10 -19 J of energy to remove an electron from an iron atom. What is the maximum wavelength of light that can do this?