Extended · Practice questions · Deflection in fields

Read the tracks.

Six original Cambridge-style questions on deflecting radiation: opposite directions, why beta bends more, the electric-field case, and identifying tracks.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

What the examiner wants

Charge sets direction, mass sets amount.

Opposite charges: alpha and beta bend opposite ways.
Mass: lighter beta bends more than heavier alpha.
No charge: gamma is not deflected.

Recall

[3 marks]

A beam of alpha, beta and gamma radiation passes through a magnetic field. State how each one is affected.

Alpha is deflected slightly in one direction. ✓
Beta is deflected more, in the opposite direction. ✓
Gamma is not deflected. ✓

Analysis

[2 marks]

Explain why alpha and beta radiation are deflected in opposite directions.

Alpha is positively charged and beta is negatively charged. ✓
The field pushes opposite charges in opposite directions. ✓

Analysis

[2 marks]

Although alpha has a larger charge than beta, beta is deflected much more. Explain why.

Beta has a much smaller mass than alpha. ✓
So the force changes the light beta’s direction far more than the heavy alpha’s. ✓

Recall

[1 mark]

Explain why gamma radiation is not deflected by a magnetic or electric field.

Gamma has no charge, so the field exerts no force on it. ✓

Application

[2 marks]

A beam of beta particles enters the space between two charged plates, one positive and one negative. State which plate the beta is deflected towards, and why.

Towards the positive plate. ✓
Beta is negatively charged, and opposite charges attract. ✓

Application

[3 marks]

Three tracks are seen as radiation crosses a magnetic field: track P is straight, track Q curves gently, and track R curves sharply the other way. Identify each track and give a reason.

P is gamma: it is not deflected because it has no charge. ✓
Q is alpha: it is charged but heavy, so it bends only a little. ✓
R is beta: it is light, so it bends a lot, in the opposite direction to alpha. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.