CAIE A-Level Physics 22.4.3 Photon Transitions: hf = E₁ − E₂

Practise calculating photon energy or frequency from discrete energy-level differences and interpreting emission or absorption transitions.

Exam points

calculate photon frequency or energy from hf = E1 − E2
interpret emission or absorption transitions and the sign or size of the energy difference

[Maximum number: 3]

(a)

Four electron energy levels in an isolated atom are shown in Fig. 12.1.

Fig. 12.1

For the emission spectrum associated with these energy levels,

[ 3 ]

(i)

on Fig. 12.1, mark with an arrow the transition that gives rise to the shortest wavelength,

[ 1 ]

(ii)

show that the wavelength of the transition in (i) is $4.35 \times 10^{-7} \mathrm{~m}$ .

[ 2 ]

$E=h c / \lambda$ or E=h f and $c=f \lambda$

\lambda=\left(6.63 \times 10^{-34} \times 3.00 \times 10^{8}\right) /\left[(3.40-0.54) \times 1.60 \times 10^{-19}\right]=4.35 \times 10^{-7} \mathrm{~m}

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