Electrons are emitted from an electron gun at almost zero velocity and

1.	Electrons are emitted from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of 1.0 m. The electrons are now scattered by an atomic hydrogen sample in ground state. What should be the minimum value of E so that red light of wavelength 656.3 nm may be emitted by the hydrogen ?
Answer» The given wavelength in Balmer series. The first line, which requires minimum energy is from n₁ = 3 to n₂ = 2. The energy should be equal to the energy required for transition from ground state to n = 3. i.e. E = 13.6 [1 – (1/9)] = 12.09 eV Minimum value of electric field = 12.09 v/m = 12.1 v/m

Electrons are emitted from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of 1.0 m. The electrons are now scattered by an atomic hydrogen sample in ground state. What should be the minimum value of E so that red light of wavelength 656.3 nm may be emitted by the hydrogen ?

Answer»

The given wavelength in Balmer series.

The first line, which requires minimum energy is from n₁ = 3 to n₂ = 2.

The energy should be equal to the energy required for transition from ground state to n = 3.

i.e. E = 13.6 [1 – (1/9)] = 12.09 eV

Minimum value of electric field = 12.09 v/m = 12.1 v/m