Question

Electrons are ejected from sodium metal by any light that has a wavelength shorter than 544 nm. What is the kinetic energy of an electron (in J) that is ejected from sodium by light with a wavelength of 485 nm?

Answer 1

Answer:

KE=2.3 x 10⁻¹⁹ J

Explanation:

Given that

λ = 544 nm

λ' = 485 nm

The kinetic energy KE given as

KE= E - Ф

Where

$E=\dfrac{hC}{\lambda'}$

$\phi=\dfrac{hC}{\lambda}$

h= 6.626 x 10⁻³⁴

C=3 x 10⁸ m/s

Now by putting the values

$KE=\dfrac{hC}{\lambda'}-\dfrac{hC}{\lambda}$

$KE=\dfrac{34.34\times 10^{-34}\times 3\times 10^8}{485\times 10^{-9}}- \dfrac{34.34\times 10^{-34}\times 3\times 10^8}{544\times 10^{-9}}$

KE=2.3 x 10⁻¹⁹ J

This is kinetic energy.