It takes 7.21 1019 J of energy to remove an electron from an iron atom. What is the maximum wavelength of light that can do this

2.75 × 10^-45 m

Explanation:

From;

E= hc/wavelength

h= Plank's constant= 6.6 × 10^-34 Js

c= speed of light=3× 10^8 ms-1

Wavelength = 6.6 × 10^-34 × 3× 10^8/7.21 × 10^19

Wavelength= 2.75 × 10^-45 m

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