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S5 Physics: Lenses Practice Paper 1
S5 Physics: Lenses Practice Paper 1
Paper one starts with straight substitution into 1/v = 1/f – 1/u: the same-size image at u = 2f, the magnified image with the object between f and 2f, the diminished image beyond 2f, then the virtual image inside the focal length, and ends with image height and the inside-focal-length trap.
Quick answer 15 cm at 0.5, 20 cm at 1, 7.5 cm at 0.5, magnification 2, 60 cm at 3, 18 cm at 0.5, -40 cm at 5, image height 6 cm, 33.3 cm at 1.33, and -10 cm meaning a virtual image.
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 has a focal length of 10 cm and the object is 30 cm in front of it. Find the image distance.
- FoundationFor a convex lens of focal length 10 cm and an object at 20 cm, find the image distance and magnification.
- FoundationA convex lens of focal length 5 cm has an object at 15 cm. Find the image distance and magnification.
- FoundationWhen the object distance is 12 cm and the image distance is 24 cm, what is the magnification?
- IntermediateA convex lens of focal length 15 cm has an object at 20 cm. Find the image distance and magnification.
- IntermediateA convex lens of focal length 12 cm has an object at 36 cm. Find the image distance and magnification.
- IntermediateA convex lens of focal length 10 cm has an object 8 cm in front of it. Find the image distance and magnification.
- ChallengeAn object 3 cm tall stands 15 cm from a convex lens of focal length 10 cm. Find the image distance and image height, and state the nature of the image.
- ChallengeA convex lens of focal length 20 cm has a 2 cm object at 50 cm. Find the image distance, magnification and image height (three significant figures).
- Error redoA convex lens of focal length 10 cm has an object 5 cm away. A student answers “image distance 10 cm, real image”. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 15 cm (1/v = 1/10 – 1/30 = 1/15) | Use 1/v = 1/f – 1/u with a real object distance positive. |
| 2 | Image distance 20 cm, magnification 1 (inverted real image, same size) | At u = 2f the image is real, inverted and the same size, a useful check. |
| 3 | Image distance 7.5 cm, magnification 0.5 | The further the object, the smaller the image and the closer it sits to the focal point. |
| 4 | 2 (24 / 12) | Magnification is image distance over object distance, or image height over object height. |
| 5 | Image distance 60 cm, magnification 3 (inverted, magnified real image) | With the object between f and 2f the image is real, inverted and magnified beyond 2f. |
| 6 | Image distance 18 cm, magnification 0.5 | Beyond 2f the image is real, inverted and diminished, lying between f and 2f. |
| 7 | Image distance -40 cm (virtual), magnification 5 | An object inside the focal length gives a negative image distance: virtual, upright and magnified, the magnifying glass case. |
| 8 | Image distance 30 cm, image height 6 cm, inverted magnified real image | Find the magnification v/u = 2, multiply by the object height; a real image can be caught on a screen. |
| 9 | Image distance about 33.3 cm, magnification about 0.667, image height about 1.33 cm | Here 1/v = 1/20 – 1/50 = 3/100, so v = 100/3 cm and not a whole number. |
| 10 | Image distance -10 cm, magnification 2, upright virtual image | An object inside the focal length never gives a real image; a negative distance means the image is on the same side as the object. |
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.
