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Light helps us see when it reaches our eyes. A light source produces light; many ordinary objects are visible because they reflect light from a source. To explain a diagram, trace the path from the source, through any interaction with an object, and finally towards the eye or screen.
This Primary 4 Science guide builds a complete study sequence around seeing objects, straight-line travel, materials and shadows. It includes original comparisons and practice answers. Start by distinguishing a source from a reflecting object before tackling a shadow investigation.
Valour Primary's Science overview includes light and shadows in its P4 programme. MOE's 2023 Primary Science syllabus is the national reference; direct syllabus access has presented a verification screen, so a complete PDF audit is not claimed. School sequences vary. These activities are original study support, not official examination questions.
The Sun and a switched-on lamp produce light. A book and a wall can reflect light reaching them, but they are not themselves producing that light in the same way.
Brightness alone does not establish that an object is a source. A mirror can appear bright because it reflects a lamp's light. Ask where the light originally came from before labelling the mirror a source.
For a book in a lit room, light travels from a source to the book and some reflected light reaches the observer's eyes. Both parts of the path matter. A book in a completely dark room does not become visible merely because the eyes are open.
Do not draw an arrow showing light coming out of the eye towards the book. In this simple model, the eye receives light. Use words alongside arrows so the direction and each object's role remain clear.
In the usual primary-school model for light travelling through uniform air, light travels in straight lines. This helps explain why aligned holes can allow a beam through several cards while moving one card blocks that direct path.
Do not explain a blocked path by saying light automatically curves around the card to reach the target. Advanced optical effects are outside this beginner model. Use the stated setup and the paths that the diagram actually allows.
A transparent material allows much light through and can allow a clear view. A translucent material allows some light through but scatters it, so the view is unclear. An opaque material does not allow light through in the classroom model.
For a comparison, use the same source and similar conditions. A thicker sample may behave differently from a thinner one. Identify the tested sample rather than declaring that every form and thickness of a named material behaves identically.
Place an opaque card between a small light source and a screen. The card blocks some light, producing a darker region on the screen. The shadow is a region receiving less light, not another object leaving the card.
Mark source, blocker and screen first. Then trace paths along the blocker's edges. For a more focused explanation, continue to the existing light path and shadow guide. This lesson connects that mechanism to the broader P4 study sequence.
With a small fixed source and a fixed screen, move the same card closer to the source while keeping its orientation unchanged. Its shadow on the screen generally becomes larger in this setup. The source, object and screen positions explain the comparison.
Do not generalise the result to every possible light source or arrangement. Moving the screen instead changes another relationship. In a fair investigation, identify the one distance being varied and keep the others and the card's orientation controlled.
- Is a book reflecting a lamp's light a light source in this example?
- Describe the light path that makes the book visible.
- A sample allows some light through but gives an unclear view. Which material category fits?
- Why does an opaque card cast a shadow on a screen behind it?
- In the fixed-source, fixed-screen setup above, what must remain the same when testing the card's distance from the source?
Answers: 1. No; it reflects the lamp's light. 2. Source to book, then reflected light from book to eye. 3. Translucent. 4. It blocks some light, leaving a darker region on the screen. 5. Keep the source and screen fixed, use the same card and maintain its orientation; vary only the intended distance.
Name the source, decide whether light passes through, reflects or is blocked, then explain the observed result. If an arrow points the wrong way, repair the drawing before adding a written explanation.
Use an ordinary low-power classroom torch only with appropriate supervision if carrying out a school-approved activity. Do not look directly at the Sun or shine lights into anyone's eyes; lasers are unnecessary. Diagrams and verbal explanations are sufficient for the independent practice here.