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Photoelectric effect — KCSE Physics

KCSE Physics · 106 practice questions · 4 syllabus objectives

29 easy40 medium37 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Describe experiments to illustrate photoelectric effect and explain factors affecting it

Define threshold frequency, work function and electron volt and apply E = hf

Explain photoelectric emission using Einstein's equation and describe applications

Calculate photon energy, maximum kinetic energy, stopping potential and velocity of photoelectrons

Sample Questions

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1
easySHORT ANSWER4 marks

Define the term 'work function' and describe its significance in the context of the photoelectric effect. (4 marks)

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Part (a) — 1 mark
The minimum energy required to remove an electron from the surface of a material (1 mk)
Part (b) — 3 marks
Determines whether photoelectric emission will occur depending on the energy of incoming photons (1 mk)
Affects the threshold frequency of light needed for emission (1 mk)
Different materials have different work functions, influencing their photoelectric properties (1 mk)
2
easySHORT ANSWER4 marks

Explain how Einstein's equation relates to the photoelectric effect. (4 marks)

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Part (a) — 1 mark
E = hf - φ (where E is the energy of the emitted electron, hf is the energy of the photon, and φ is the work function) (1 mk)
Part (b) — 3 marks
E is the maximum kinetic energy of the emitted electrons (1 mk)
hf is the energy of the incident photon, determined by its frequency (1 mk)
φ is the minimum energy required to release an electron from the material (1 mk)
3
easySHORT ANSWER3 marks

Define the photoelectric effect and give two examples of its applications in modern technology. (3 marks)

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Part (a) — 1 mark
The emission of electrons from a material when it absorbs light energy (1 mk)
Part (b) — 2 marks
Photovoltaic cells for solar energy conversion (1 mk)
Photoelectric sensors in automatic doors (1 mk)
4

Define the term 'work function' in the context of the photoelectric effect and describe its importance in determining if photoemission will occur. (4 marks)

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