waec model questions vol1 2019 physics
Objective • Question 14
Question 14
WAEC_MODEL_QUESTIONS_VOL1
•
2019
An electron in a hydrogen atom is initially in the n = 3 level. It absorbs a photon and jumps to the n = 5 level. It is then ionized by absorbing another photon of wavelength λ. (Take R = 1.097 × 10⁷ m⁻¹, h = 6.626 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, and 1 eV = 1.602 × 10⁻¹⁹ J.) After ionization, the free electron is accelerated through a potential difference of 150 V. Determine (i) the wavelength λ of the ionizing photon (in nm) and (ii) the de Broglie wavelength of the accelerated electron (in pm).
Answer Options
A.
2.28×10^3 nm, 120 pm
Correct Answer
B.
2.28×10^3 nm, 100 pm
C.
2.15×10^3 nm, 110 pm
D.
2.40×10^3 nm, 90 pm
Correct Answer
B
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