Question

What is the maximum kinetic energy of an ejected electron if magnesium metal is irradiated with 294 nm light? The threshold wave length for a magnesium metal surface is 339nm.

Answer #2

The energy is given by the formula

E = hc/ L

h is the planck's constant = 6.63 x 10^{-34} J/s

c is the speed of light = 3 x 10^{8} m / s

L is the wavelength = 294 nm or 2.94 x 10^{-7} m

putting all the values,

E = (6.63 x 10^{-34} x 3 x 10^{8}) / 2.94 x
10^{-7}

E = 6.76 x 10^{-19} J

The threshold energy will be given as

E = (6.63 x 10^{-34} x 3 x 10^{8}) / 3.39 x
10^{-7}

E = 5.87 x 10^{-19} J

The difference of these energies goes in the Kinetic energu of electron

So KE of electron = (6.76 x 10^{-19}) - (5.87x
10^{-19})

= 8.9 x 10^{-20} J

answered by: anonymous

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