Question

A metal surface is illuminated by a radiation of wavelength 4500 Å. The rejected photo-electron enters a constant magnetic field of 2 mT making an angle of 90° with the magnetic field. If it starts revolving in a circular path of radius 2 mm, the work function of the metal is approximately:

• A. 1.36 eV
• B. 1.69 eV
• C. 2.78 eV
• D. 2.23 eV

Answer 1

Answer: (A)

1.36 eV

Answer 2

The correct answer is (A): 1.36 eV

Explanation:

$\frac{hc}{λ}$ - Ø = ΚΕ........(i)
R =$\frac{ mv}{Bq}$ = $\sqrt{\frac{2m(KE)}{Bq }}$ ........(ii)
Putting the values,

Ø ≃ 1.36 eV