A light of wavelength 400 nm is incident on a metal surface with work function 2 eV. What is the sto

JAMB Physics 2023 74 views

A light of wavelength 400 nm is incident on a metal surface with work function 2 eV. What is the stopping potential of the photoelectrons emitted?

[c = 3 x 10⁸ ms⁻¹, e = 1.6 x 10⁻¹⁹ C, h = 6.63 x 10⁻³⁴ Js]

  1. 1.11 V ✓
  2. 2.43 V
  3. 2.12 V
  4. 1.48 V

Explanation

Step 1: Identify given values and what to find
Given: λ = 400 nm = 4 × 10⁻⁷ m, W = 2 eV, h = 6.63 × 10⁻³⁴ Js, c = 3 × 10⁸ ms⁻¹
Find: Stopping potential V_s

Step 2: Calculate photon energy
Formula: E = hc/λ
E = (6.63 × 10⁻³⁴ × 3 × 10⁸)/(4 × 10⁻⁷)
E = (1.989 × 10⁻²⁵)/(4 × 10⁻⁷) = 4.97 × 10⁻¹⁹ J

Step 3: Convert to eV
E = 4.97 × 10⁻¹⁹ / 1.6 × 10⁻¹⁹ = 3.11 eV

Step 4: Calculate stopping potential
Formula: V_s = (E – W)/e
V_s = 3.11 – 2 = 1.11 V

Step 5: The answer is 1.11 V

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