Question

If the electron in hydrogen atom jumps from second Bohr orbit to ground state and difference between energies of the two states is radiated in the form of photons. If the work function of the material is 4.2 eV, then stopping potential is ______.

[Energy of electron in nth orbit = `-13.6/"n"^2` eV ]

Options

• 2V

• 4V

• 6V

• 8V

Answer 1

If the electron in hydrogen atom jumps from second Bohr orbit to ground state and difference between energies of the two states is radiated in the form of photons. If the work function of the material is 4.2 eV, then stopping potential is 6V.

Explanation:

Energy difference between two states

`Delta"E" = "E"_2-"E"_1=(-13.6)/2^2-((-13.6)/1^2)`

`Delta=13.6/1^2-13.6/2^2`

`Delta=13.6[(4-1)/4]=13.6xx3/4`

∴ ΔE = 10.2 eV

Since, the energy is radiated in form of photons,

∴ Energy of photons = hv = 10.2 eV

From Einstein's photoelectric equation,

hv = Φ₀ + eV_s

10.2eV = 4.2eV + eV_s

⇒ 6 eV = eV_s

∴ V_s = 6V