Case study·Standard multi-step (3/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
In an optics practical, a student gets a sharp image for a convex lens at several object distances, but two points on the versus graph are visibly off the straight-line trend.
Total: 4 marks
(a) Should the student draw a best-fit straight line or a zig-zag line through all points? (1 mark)
(b) Name one possible cause of the two off-trend points. (1 mark)
(c) Which graph feature is used to obtain focal length? (1 mark)
(d) Why is a sharp image essential before noting ? (1 mark)
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