NEET 2017 · PhysicsEinstein eq.Previous Year Question
The photoelectric threshold wavelength of silver is 3250 × 10⁻¹⁰ m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 × 10⁻¹⁰ m is (Given h = 4.14 × 10⁻¹⁵ eV·s and c = 3 × 10⁸ m/s):
Answer: (B) 0.6 × 10⁶ m/s. Answer: (b) 0.6 × 10⁶ m/s Solution: φ = hc/λ₀ = 1240/325 ≈ 3.82 eV.
- A.6 × 10⁵ m/s
- B.0.6 × 10⁶ m/s✓
- C.61 × 10³ m/s
- D.0.3 × 10⁶ m/s
Correct Answer
(B) 0.6 × 10⁶ m/s
Solution & Explanation
Answer: (b) 0.6 × 10⁶ m/s Solution: φ = hc/λ₀ = 1240/325 ≈ 3.82 eV. E = hc/λ = 1240/253.6 ≈ 4.89 eV. Kmax = 4.89 − 3.82 ≈ 1.07 eV = ½mv² ⇒ v ≈ 0.6 × 10⁶ m/s.
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