Predict nuclear emission deflection in a magnetic field
Combine initial motion field direction and charge sign while keeping gamma undeflected in the stated model.
Exam scope and assessment notes
Extended only (Supplement) · Physics 0972, 2026–2028. Use labelled nuclides, supplied count intervals and stated background conditions. Model drawings are not to scale. Written practice is self-checked. Human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0972 has the same subject content as IGCSE 0625, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Use perpendicular motor directions.
- Know alpha and beta-minus signs.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
For rightward beta-minus motion and inward field, which initial force is correct?
What you will learn
- Combine initial motion field direction and charge sign while keeping gamma undeflected in the stated model.
- Determine magnetic deflection with charge-aware motion and preserve the no-work and schematic-path limits.
Fix all three direction inputs
For rightward motion into a page-inward magnetic field, a positive alpha beam has initial force upward. A beta-minus electron beam moving rightward has the opposite conventional-current contribution and initial force downward. Gamma has no charge-based magnetic deflection in this simple comparison.
Use a fixed right/up/out-of-page frame and show inward magnetic field by crosses. Reversing only the field reverses both charged-beam force directions. Reversing both velocity and field restores the original force senses for unchanged charges.
Keep the force and energy accounts separate
The ideal magnetic force is perpendicular to instantaneous particle velocity. It changes the motion direction without doing work along that motion, so magnetic bending alone does not prove an increase in speed or kinetic energy. Other interactions can transfer energy and must be analysed separately.
A supplied initial-force sketch is not a full orbit solution. Curvature magnitude needs particle mass, charge magnitude, speed and field information. Gamma’s straight path under the specified electric and magnetic comparisons distinguishes its charge response, but does not certify a material as transparent to gamma radiation.
Pause and explain
Does magnetic bending alone show that the field increased particle kinetic energy?
Worked example
Rightward alpha, beta-minus and gamma enter an inward magnetic field. State initial deflections.
Show the worked solution
- Positive-charge motion gives upward force.
- Negative beta-minus charge reverses it.
- Gamma has no charge-based magnetic deflection.
Answer Alpha up; beta-minus down; gamma undeflected.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Give initial force on alpha moving rightward in an inward magnetic field.
Give me a hint
Use positive-charge motion and the motor direction relationship.
Compare my reasoning
- Motion is rightward.
- Field is inward.
- The positive-charge force is upward.
Upward.
Look for these in your work
- Fix motion and field.
- Retain alpha’s positive sign.
Reverse only the inward field to outward and find beta-minus force.
Give me a hint
A single field reversal reverses the original force.
Compare my reasoning
- Original beta-minus force was down.
- Field alone reverses.
- The new force is up.
Upward.
Look for these in your work
- Retain rightward motion.
- Change only the named input.
A diagram shows equal alpha and beta bends and claims this proves equal masses. Critique it.
Give me a hint
Separate schematic paths from calibrated particle evidence.
Compare my reasoning
- The paths may be symbolic.
- Curvature also depends on charge magnitude, speed and field.
- Equal-looking bends do not determine equal masses.
The schematic does not establish equal alpha and beta masses.
Look for these in your work
- Name missing physical data.
- Avoid extracting a mass from illustration alone.
Common mistakes
- Motion direction differs from electron conventional current.
- Keep into-page symbols explicit.
- Bending alone is not speeding-up.
What can you explain now?
What does a cross represent in the page-field convention?
Compare with the explanation
Into the page
The cross marks an arrow directed away from the observer, into the page.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Determine magnetic deflection with charge-aware motion and preserve the no-work and schematic-path limits.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.