Radioactivity — KCSE Physics

KCSE Physics · 107 practice questions · 10 syllabus objectives

36 easy36 medium35 hard

What You'll Learn

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

State hazards of radiation, precautions, shielding, background radiation, and applications

Compare the properties (charge, mass, ionising power, penetrating power) of alpha (α), beta (β) and gamma (γ) radiation

Apply the half-life formula (N = N₀ × (½)ⁿ) to calculate the remaining quantity of a radioactive isotope after n half-lives

Write balanced nuclear equations for alpha decay, beta decay and nuclear fission/fusion reactions

Define radioactive decay, isotope, and half-life; calculate decay and remaining atoms from half-life data

Identify alpha, beta, and gamma radiation by penetration, deflection, and ionisation; compare X-rays and gamma rays

Describe detectors of radiation including the Geiger-Muller tube

Explain nuclear fission, fusion, and chain reactions in a nuclear reactor

Balance nuclear equations; determine missing mass/atomic numbers and count alpha/beta emissions

Radioactivity

Sample Questions

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1
easySHORT ANSWER4 marks

Name two types of radiation detectors and briefly describe how each functions. (4 marks)

View Marking Scheme
Part (a) — 2 marks
Geiger-Muller tube (1 mk)
Scintillation counter (1 mk)
Part (b) — 2 marks
The Geiger-Muller tube detects radiation by ionising gas within the tube, producing a pulse of current. (1 mk)
The scintillation counter detects radiation by using special crystals that emit light when struck by radiation, which is then converted to an electrical signal. (1 mk)
2
easySHORT ANSWER3 marks

Name the type of radiation that can be deflected by a magnetic field and explain why this occurs. (3 marks)

View Marking Scheme
Part (a) — 1 mark
Beta radiation (1 mk)
Part (b) — 2 marks
Beta particles are charged (negative charge) (1 mk)
Charged particles experience a force in a magnetic field, causing them to deflect (1 mk)
3
easySHORT ANSWER3 marks

State the balanced nuclear equation for the alpha decay of radium-226. (3 marks)

View Marking Scheme
Part (a) — 3 marks
Ra-226 → Rn-222 + He-4 (3 mks)
4

A radioactive isotope has a half-life of 5 years. If the initial quantity of the isotope is 80 grams, calculate the remaining mass after 15 years. (3 marks)

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Why Practise Radioactivity?

KNEC Aligned

Questions match the KCSE syllabus objectives and exam format exactly.

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