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S5 Physics: Lenses Practice Paper 2
S5 Physics: Lenses Practice Paper 2
Paper two drills 1/v = 1/f − 1/u and the magnification ratio, starting with clean integer cases at and beyond 2f, then short focal lengths, then long image distances just outside f and image-height conversion, ending with the u minus f blunder.
Quick answer 24 cm and 1, 13.5 cm and 0.5, 24 cm and 3, 48 cm and 2, 12 cm and 3, 30 cm and 2, 22.5 cm and 0.5, 100 cm and 4, 36 cm and a 12 cm image, and the virtual minus 24 cm case.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Physics: Lenses – Tutor Lesson Plan |
| Level | S5 |
02 Questions (10 items)
- FoundationA convex lens of focal length 12 cm has an object 24 cm in front of it. Find the image distance and the magnification.
- FoundationA convex lens has focal length 9 cm and the object is 27 cm away. Find the image distance and magnification.
- FoundationA convex lens of focal length 6 cm has an object 8 cm in front of it. Find the image distance and magnification.
- FoundationA convex lens with focal length 16 cm has an object 24 cm away. Find the image distance and magnification.
- IntermediateA convex lens has focal length 4 cm and an object 6 cm in front. Find the image distance and magnification.
- IntermediateA convex lens of focal length 10 cm has an object 15 cm away. Find the image distance and magnification.
- IntermediateA convex lens of focal length 15 cm has an object 45 cm in front. Find the image distance and magnification.
- ChallengeA convex lens with focal length 20 cm has an object 25 cm away. Find the image distance and magnification.
- ChallengeA convex lens of focal length 9 cm has a 4 cm tall object 12 cm in front. Find the image distance, magnification and image height.
- Error redoA convex lens has focal length 12 cm and the object is 8 cm in front. A student answers “v = 12 − 8 = 4 cm”. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Image distance 24 cm, magnification 1. | When the object sits at 2f the image also forms at 2f and is the same size. |
| 2 | Image distance 13.5 cm, magnification 0.5. | Beyond 2f the image is inverted and diminished, forming between f and 2f. |
| 3 | Image distance 24 cm, magnification 3. | Between f and 2f the image is inverted and magnified. |
| 4 | Image distance 48 cm, magnification 2. | Always use 1/v = 1/f − 1/u rather than guessing v as u minus f. |
| 5 | Image distance 12 cm, magnification 3. | The shorter the focal length, the greater the magnification at the same object distance. |
| 6 | Image distance 30 cm, magnification 2. | At an object distance of 1.5f the magnification is exactly 2, a handy check. |
| 7 | Image distance 22.5 cm, magnification 0.5. | The further the object, the closer the image sits to the focal point and the smaller the magnification. |
| 8 | Image distance 100 cm, magnification 4. | Just beyond f the image distance grows sharply, which is the expected result. |
| 9 | Image distance 36 cm, magnification 3, image height 12 cm. | Work out the magnification first, then multiply by the object height. |
| 10 | A virtual image at v = −24 cm with magnification 3 on the same side as the object. | Inside the focal length the image is virtual; u minus f is not a formula for v. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.
