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P3 General Studies: Light and Shadows (Paper 4 (error clinic))
Tutor Prep Guide · straight-line light, shadow direction and length, reflection angles and the normal, sundials and pinhole images
P3 General Studies: Light and Shadows (Paper 4 (error clinic))
Paper four targets past errors: shadow on the same side as the source, measuring angles from the surface, inverted ratios and treating shadows as made by the object.
Direct answers Write the source position or the normal first, then draw, and only then calculate.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: P3 General Studies: Light and Shadows |
| Level | parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety |
02 Questions (10 items)
- FoundationWhen the Sun is in the west, where is the shadow?
- FoundationWith an angle of incidence of 50 degrees, what is the angle between the two rays?
- FoundationWhat mainly decides how long a shadow is?
- IntermediateIn 12 trials the shadow fell opposite the source 9 times. What percentage is that?
- IntermediateA 0.8 m object casts a 1.6 m shadow. What is the ratio of height to shadow length?
- IntermediateIs a pinhole image upright or inverted, and why?
- ChallengeLight travels at about 299792458 m/s. Must a P3 pupil memorise this number?
- ChallengeAmong glass, clear water and a wooden door, which is opaque?
- ChallengeA pupil measures the same pencil shadow in the morning and at noon. Which is longer?
- Error redoA classmate says a shadow is made by the object itself and so sits under the feet. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | On the east side | A shadow always falls opposite the source, so a western Sun gives an eastern shadow. |
| 2 | 100 degrees | The angle of reflection is also 50 degrees, and 50 plus 50 gives 100 degrees. |
| 3 | The angle and position of the light source, not the size of the object | The same object casts different shadow lengths as the source moves, so the source angle is the deciding factor. |
| 4 | 75.0 Percentage points | Nine divided by twelve times one hundred gives 75.0 percentage points. |
| 5 | 0.5 | Zero point eight divided by one point six equals 0.5. |
| 6 | Inverted, because straight-line light crosses behind the hole | Light travels straight through the hole, so rays from the top land at the bottom and the image is inverted. |
| 7 | No. It is background information; pupils only need to know light is very fast | The number is background only, and the lesson only requires using straight-line light to explain the phenomena. |
| 8 | The wooden door | Glass and clear water let light through while the wooden door does not, so a shadow forms behind the door. |
| 9 | The morning one, because the Sun is lower | A lower Sun gives a longer shadow, so the morning shadow exceeds the noon shadow. |
| 10 | A shadow is caused by blocked light and lies opposite the source | A shadow is not produced by the object; it is the unlit region behind where straight-line light is blocked. |
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.
With all four done, go back to the chapter page and revise the three parts of a closed circuit plus three safety habits.Tutor Registration →
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