The mean free path of electrons in a metal is 4 X 10⁻⁸ m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in the units V/m,
The energy gained by an electron in an electric field
E over a mean free path l is given by:
eEl = 2 eV
Solving for E:
E = 2 × 1.6 × 10⁻¹⁹ /4 × 10⁻⁸ = 8 × 10⁷ V/m
Thus, the correct answer is (d) 8 × 10⁷ V/m.
Class 12th Science Physics NCERT MCQ Questions
NCERT Books MCQ Questions Session 2024-2025.
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The energy gained by an electron in an electric field E over a mean free path λ is given
by:
eEλ=2 eV
Substituting e = 1.6 × 10⁻¹⁹ C and
λ = 4 × 10 m:
E = 2 1.6 × 10⁻¹⁹/4 × 10⁻⁸
E = 8 × 10⁷ V/m
Thus, the correct answer is (d) 8 × 10⁷ V/m.
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