A photosensitive metallic surface has work function, h 0. If photons of energy 2h 0 fall on this surface, the electrons come out with a maximum velocity of 4 106 m/s. When the photon energy is increased to 5h 0, then maximum velocity of photoelectrons will be
- 2 107 m/s
- 2 106 m/s
- 8 106 m/s
- 8 105 m/s
Answer
(3) 8 106 m/s
Solution
Einstein's photoelectric equation: 12mvmax2 = E - h 0
Case 1: 12mv12 = 2h 0 - h 0 = h 0
Case 2: 12mv22 = 5h 0 - h 0 = 4h 0
v22v12 = 4 ⇒ v2 = 2v1
v2 = 2 4 106 = 8 106 m/s
Answer: (3)