A-LevelPhysicsQuantum physics9702/42 · May/June 2017 · Q109 Marks

Briefly describe two phenomena associated with the photoelectric effect that cannot be explained using a wave theory of light. 1. ..................................................................................................................................................... 2. ..................................................................................................................................................... [2]

(a)Briefly describe two phenomena associated with the photoelectric effect that cannot be explained using a wave theory of light. 1. ..................................................................................................................................................... 2. ..................................................................................................................................................... [2][2]
(b)(i)Identify the symbol λ₀.[1]
(b)(ii)1.Use Fig. 10.1 to determine the magnitude of λ₀. λ₀ = ............................................................................ m [1][1]
(b)(ii)2.Use the gradient of Fig. 10.1 to determine a value for the Planck constant h. h = ........................................................................... J s [3][3]
(c)The metal surface in (b) becomes oxidised. Photoelectric emission is still observed but the work function energy is increased. On Fig. 10.1, draw a line to show the variation with ¹/λ of E_MAX for the oxidised surface. [2][2]

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Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

[B2] two from: ∞ frequency below which electrons not ejected ∞ maximum energy of electron depends on frequency ∞ maximum energy of electrons does not depend on intensity ∞ instantaneous emission of electrons
[B1] (λ₀ is the) threshold wavelength or wavelength corresponding to threshold frequency or maximum wavelength for emission of electrons
[A1] intercept = 1/λ₀ = 2.2 × 10⁶ m⁻¹ λ₀ = 4.5 × 10⁻⁷ m or 450 nm
[C1] gradient = hc
[C1] gradient = 2.0 × 10⁻²⁵ or correct substitution into gradient formula
[A1] h = (2.0 × 10⁻²⁵) / (3.0 × 10⁸) = 6.7 × 10⁻³⁴ J s
[B1] line: same gradient
[B1] straight line, positive gradient, intercept at greater than 2.2 × 10⁶ when candidate's line extrapolated

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