Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a phototsensitive material. he stopping potential is measured to be 3.57 V. The threshold frequency of the materials is:

Options

(a) 4 x 10¹⁵ Hz
(b) 5 x 10¹⁵ Hz
(c) 1.6 x 10¹⁵ Hz
(d) 2.5 x 10¹⁵ Hz

Correct Answer:

1.6 x 10¹⁵ Hz

Explanation:

n → 2 – 1 E = 10.2 eV kE = E – ?
Q = 10.20 – 3.57 h u₀ = 6.63 eV
u₀ = 6.63 x 1.6 x 10⁻¹⁹ / 6.67 x 10⁻³⁴
= 1.6 x 10¹⁵ Hz