# Sodium has a work function of 2.3eV. Given that: Planck’s constant h = 6.63 x 10-34JS, velocity of light in vacuum, C = 3.0 x 108m/s, 1 electron-volt (1eV) = 1.6 x 10-19 C and mass of an electron, me = 9.1 x 10-31kg, calculate:

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Sodium has a work function of 2.3eV. Given that: Planck’s constant h = 6.63 x 10-34JS, velocity of light in vacuum, C = 3.0 x 108m/s, 1 electron-volt (1eV) = 1.6 x 10-19 C and mass of an electron, me = 9.1 x 10-31kg, calculate:

1. its threshold frequency.
2. the maximum velocity of the photoelectrons produced when the sodium is illuminated by light of wavelength 5.0 x 10-7m.
3. the stopping potential V, with the light of this wavelength.

1. hfo = wo
6.63 x 10-34fo=2.3 x 1.6 x10-19
fo = 5.55 x 1014HZ

2. hf = wo + 1/2MV2
h c/λ = Wo + 1/2MV2
6.63 x 10-34 x      3.0x108   = 2.3 x 1.6 x 10-19 + 1/2MV2
5.0 x 10-7
3.978 x 10-19 = 3.68 x 10-19 + 1/2MV2
1/2MV2 = 0.298 x 10-19

3. eVs = 1/2MV2
1.6 x 10-19Vs = 0.298 x 10-19
Vs0.298 x 10-19
1.6 x 10-19
=0.186Volts