A photoemissive substance is illuminated with a radiation of wavelength i so that it releases electrons with de-Broglie wavelength e. The longest wavelength of radiation that can emit photoelectron is o. Expression for de-Broglie wavelength is given by: (m: mass of the electron, h: Planck's constant and c: speed of light)
- e = h i 2mc
- e = h 2mc ( 1 i - 1 o )
- e = h2mc ( 1 i - 1 o )
- e = h o2mc
Answer
(3) e = h2mc ( 1 i - 1 o )
Solution
Work function: 0 = hc o (threshold wavelength o).
Einstein's photoelectric equation:
K = hc i - hc o = hc ( 1 i - 1 o )
de Broglie wavelength of the electron:
e = h 2mK = h 2m hc ( 1 i - 1 o )
e = h22mhc ( 1 i - 1 o ) = h2mc ( 1 i - 1 o )
Answer: (3)