In a photoelectric experiment, photoelectrons are emitted with a maximum kinetic energy of 3.2 × 10⁻¹⁹ J. What minimum stopping potential is required to reduce the photocurrent to zero? (Elementary charge e = 1.6 × 10⁻¹⁹ C)
Answer and explanation
Correct answer: D. 2.0 V
- Step 1: Stopping potential formula: e Vs = K_max. Step 2. Rearrange: Vs = K_max / e. Step 3. Compute: Vs = (3.2 × 10⁻¹⁹) / (1.6 × 10⁻¹⁹) = 2.0 V. Answer: 2.0 V. Why not the others: 1.6 V uses elementary charge value; 3.2 V uses K_max directly; 0.5 V inverts the quotient.
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