Radiation of wavelength , is incident on a photocell. The fastest emitted electron has speed v. If the wavelength is changed to , the speed of the fastest emitted electron will be :
- (A)
- (B)
- (C)
- (D)✓ Correct
Answer: (D)
Solution
Einstein's equation gives at the first wavelength and at the shorter one. Subtracting, . So , which exceeds because the work-function term is positive. The new speed is therefore greater than .
JEE Main · 2016 · 03 Apr 2016 · Offline · Single correct option