Question

Threshold frequency of a metal is 5 × 10¹³ s^-1 upon which 1 × 10¹⁴ s^-1 frequency light is focused. Then the maximum kinetic energy of emitted electron is

• A. 3.3 × 10^-21
• B. 3.3 × 10^-20
• C. 6.6 × 10^-21
• D. 6.6 × 10^-20

Answer 1

Answer: (B)

Following the conservation of energy principle,
Kinetic energy $\left(\frac{1}{2} m_{e}\upsilon^{2}\right)=h\left(\upsilon-\upsilon_{0} \right)$
$\quad\quad$= (6.626 × 10^-34 J s) (1 × 10¹⁴ s^-1 - 5 × 10¹³ s^-1)
$\quad\quad$ = (6.626 × 10^-34 J s) (5 × 10¹³ s^-1)
$\quad\quad$ = 3.313 × 10^-20 J