Series route: This guide belongs to the complete PSLE Learner’s Guide volume directory. The original PSLE Learning Guide supplies the wider English, Mathematics and Science route, while PSLE Science provide verified subject-specific continuation.
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This volume solves one precise learner problem: the learner sees a larger shadow and concludes that the object became larger, or moves several parts of the apparatus and attributes the change to the wrong distance. The aim is not to memorise a slogan. It is to understand the mechanism well enough to recognise the idea when the wording, numbers, diagram or context changes. A Primary 6 learner should be able to explain the decision, perform it under time pressure, and detect a tempting answer that only looks familiar.
- Understand the mechanism before memorising a form.
- Study the worked examples and compare near-misses.
- Repair common misconceptions with targeted tests.
- Complete graded independent practice before reading the answers.
- Use delayed transfer and examination control to make the skill durable.
- Use the parent and tutor notes only after the learner has attempted the work.
The problem beneath the mistake
A card can cast a small shadow in one position and a large shadow in another without changing shape or size. The change occurs in the pattern of blocked light on the screen.
A lamp sends light outward in many directions. When an object is close to the source, it blocks a wider spread of rays by the time those blocked paths reach a more distant screen.
Move the same object nearer the screen instead, while keeping lamp and screen fixed, and the shadow usually becomes closer to the object’s actual outline and smaller than when the object is near the lamp.
The shadow is not a material copy. It is a region where light from the source is blocked fully or partly. Its dimensions depend on arrangement as well as object dimensions.
The light source matters. A very small source can make a sharper shadow. An extended bulb can produce a dark central region and lighter blurred edges because different parts of the source are blocked differently.
Distance claims must name endpoints. “Closer” is incomplete unless the learner states closer to the lamp or closer to the screen. These changes often have opposite effects on shadow size.
A fair investigation fixes lamp, screen and object orientation, then changes only one selected distance. Moving both object and screen makes the cause difficult to isolate.
The object must stay perpendicular or at a recorded angle. Tilting a flat card changes the projected shape and width, creating another variable.
Ambient light can make a shadow look lighter without changing its geometric boundary. Brightness and size are related to different observations and should be measured separately.
A ruler should measure the shadow on a fixed screen, while another measurement confirms that the object’s dimensions did not change. Photographs should use a fixed camera position and scale.
The explanation should not say light bends around the object in an ordinary ray model unless diffraction is specifically relevant. At this level, straight-line travel and blocked diverging rays explain the main geometry.
The reliable routine is identify source, object and screen; mark distances; change one distance; measure shadow size; and state that the object remained unchanged.
Core decision: With a lamp, object and screen arranged in line, moving the object closer to a diverging light source can make its shadow larger on the screen even though the object’s physical size stays constant.
A useful rule has three parts: a trigger, an operation and a check. The trigger tells you when the rule applies. The operation tells you what to do. The check tells you whether the result still matches the meaning of the question. Learners who remember only the operation often apply it in the wrong place; learners who remember only an example often freeze when the surface details change.
Mechanism: why the rule works
1. Identify the three-part system
Locate the light source, opaque object and receiving screen.
Diagnostic question: What makes light, what blocks it and where is the shadow observed? Reliable response: Label all three before describing movement.
2. Name the changed distance
State whether object-to-lamp, object-to-screen or lamp-to-screen distance changes.
Diagnostic question: Closer to which reference? Reliable response: Write both endpoints and units.
3. Trace boundary rays
Imagine straight rays from the source just touching opposite edges of the object and continuing to the screen.
Diagnostic question: Where do those rays meet the screen? Reliable response: Use them to outline the shadow.
4. Separate object and projection
The object keeps its physical dimensions while the blocked region at the screen changes.
Diagnostic question: Was the object measured before and after? Reliable response: Report shadow size, not object growth.
5. Control other variables
Keep lamp, screen, object orientation, ambient light and measurement method constant.
Diagnostic question: What else could alter size or edge clarity? Reliable response: Change only the selected position.
6. Limit the conclusion
State the relationship for the tested arrangement rather than a universal rule without conditions.
Diagnostic question: Which components were fixed? Reliable response: Include source type and screen position when relevant.
Worked examples: make the decision visible
Do not race through these examples. Before reading each explanation, name the evidence that matters and the information that does not. Then compare the correct route with the tempting route. That comparison is where the transferable learning sits.
Worked example 1: Object nearer lamp
Task. A card moves from40 cm to15 cm from a lamp while the screen stays fixed.
Reasoning. The card blocks rays earlier in their outward spread, so the blocked region expands farther before reaching the screen. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. The shadow can become larger although the card is unchanged.
Independent check. Measure the card to confirm its physical size is constant. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 2: Object nearer screen
Task. The same card moves toward the screen while lamp and screen stay fixed.
Reasoning. There is less distance for the blocked ray boundary to spread after passing the card. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. The shadow becomes smaller and closer to the card’s size.
Independent check. Compare with the near-lamp position. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 3: Screen moved away
Task. Lamp and object stay fixed while the screen moves farther back.
Reasoning. Boundary rays continue diverging, so their separation at the screen increases. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. The shadow can become larger on the farther screen.
Independent check. Only screen distance changed. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 4: Tilted card
Task. A rectangular card is rotated while its centre stays at the same position.
Reasoning. Its projected width relative to the rays changes. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. A different shadow width cannot be attributed only to distance.
Independent check. Keep orientation fixed for a distance test. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 5: Larger object
Task. Two cards are at the same position but one is wider.
Reasoning. The wider object blocks a wider set of rays. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. Object size can affect shadow size when geometry is otherwise the same.
Independent check. This is a different independent variable. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 6: Extended bulb
Task. A broad bulb produces a fuzzy edge.
Reasoning. Different source points create overlapping dark and partial-shadow regions. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. Edge clarity changes even if the main shadow geometry is similar.
Independent check. Use the same source in all trials. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 7: Ambient light
Task. Room lights are switched on during the second trial.
Reasoning. Additional light fills the shadow region and reduces contrast. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. A lighter-looking shadow does not necessarily mean a smaller geometric shadow.
Independent check. Measure boundary and darkness separately. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Worked example 8: Cautious claim
Task. The shadow width rises from8 cm to12 cm when the object moves closer to the lamp.
Reasoning. The measured projection changed while the object width and other settings were controlled. The controlling idea is the geometry of light source, object and screen, especially which distances changed while the object itself remained the same. This prevents a learner from choosing an answer merely because one word, number or observation resembles a remembered example.
Answer. Under this setup, decreasing object-to-lamp distance increased shadow width.
Independent check. Repeat trials and check the distance labels. A good check approaches the conclusion from a different direction. Repeating the same steps more slowly may repeat the same hidden assumption.
Deepening lab: compare cases, conditions and limits
A method becomes independent when you can say where it applies, where it stops and which change would alter the conclusion. The cases below deliberately vary one structural feature at a time. For each case, pause before the analysis and predict whether the core rule remains available. Then name the exact condition that controls the decision. This is harder than repeating a worked solution, but it is also closer to what an unfamiliar examination item demands.
Deepening case 1: Point-like source
Case. A small source produces clear boundary rays.
Analysis. The simplified geometry gives a sharp shadow. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Draw the edge rays. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 2: Extended source
Case. A broad source creates partial-shadow zones.
Analysis. Not every source point is blocked at the same place. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Distinguish dark centre and lighter edge. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 3: Object at screen
Case. When the object nearly touches the screen, the projection approaches its outline.
Analysis. There is little distance for magnification. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Predict the width. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 4: Object at lamp
Case. Very near the source, a small movement can greatly alter angular blockage.
Analysis. Practical limits include source size and heat. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. State safe apparatus limits. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 5: Screen farther
Case. A farther screen receives the diverging boundary rays at a wider separation.
Analysis. Lamp and object positions remain the reference geometry. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Compare two screen distances. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 6: Screen nearer
Case. A nearer screen intercepts rays before they spread as far.
Analysis. The shadow can be smaller. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Hold object fixed. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 7: Bigger card
Case. A larger blocker intercepts more ray directions.
Analysis. Physical size is now the intended variable. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Design a fair size test. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 8: Same area, different shape
Case. Two objects with equal area can cast different outlines.
Analysis. Projection depends on edge geometry and orientation. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Compare circle and rectangle. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 9: Transparent object
Case. Some light passes through, so the dark region may be weak or patterned.
Analysis. Opacity affects shadow contrast. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Keep material constant. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 10: Translucent object
Case. Scattered transmitted light can soften the shadow.
Analysis. Size and darkness remain distinct observations. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Choose a measurement rule. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 11: Tilt angle
Case. A flat card’s projected width changes when tilted.
Analysis. Orientation must be controlled. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Mark the angle. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 12: Source angle
Case. Moving the lamp sideways shifts shadow position as well as size.
Analysis. Direction and distance can change together. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Use equal-radius positions for direction alone. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 13: Two lamps
Case. Each source can form its own shadow pattern.
Analysis. Overlapping shadows complicate interpretation. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Switch off one source. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 14: Outdoor sunlight
Case. Sunlight arriving nearly parallel produces different geometry from a nearby lamp.
Analysis. Source distance and angular size matter. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Avoid transferring one setup mechanically. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 15: Camera movement
Case. A camera closer to the screen can make the photographed shadow look larger.
Analysis. Image scale must be fixed for visual comparison. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Include a ruler in frame. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 16: Boundary choice
Case. A fuzzy shadow needs a stated rule for measuring width.
Analysis. Unclear endpoints reduce reliability. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Define a threshold or trace consistently. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 17: Repeated trials
Case. Moving the card back and forth tests repeatability.
Analysis. Consistent measurements support reliability. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Record average and variation. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 18: Object unchanged
Case. The same card can be measured before and after.
Analysis. Direct measurement blocks the growth misconception. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Add this control. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 19: No causal overreach
Case. One arrangement supports one conditional relationship.
Analysis. Source type and fixed distances belong in the claim. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Write the condition. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Deepening case 20: Final audit
Case. Source, object, screen, distances, orientation, measurement and claim complete the reasoning.
Analysis. Each prevents a different geometry error. Notice that the answer depends on the geometry of light source, object and screen, especially which distances changed while the object itself remained the same; changing a decorative detail would not be enough to change the reasoning.
Challenge. Audit three diagrams. State the conclusion in one precise sentence, then add one sentence that names the evidence or relationship that makes it valid.
Finish the lab with a blank-page recall. Write the rule, its conditions, one confirming example, one near-miss and one independent check from memory. Compare that page with the article only after finishing. If the rule is correct but the condition is missing, the learning is not yet safe: an overgeneralised rule can produce confident errors. If the condition is correct but no example can be generated, practise construction rather than rereading.
Common misconceptions and targeted repairs
Misconception 1: Larger shadow means larger object
What the learner may think. Projection size directly measures physical growth.
Why it fails. Geometry can magnify the blocked region. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Measure object and shadow separately. Use this short test immediately: Which quantity changed?
Misconception 2: Closer always means larger
What the learner may think. Any decrease in distance increases shadow size.
Why it fails. Closer to lamp and closer to screen are different changes. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Name both endpoints. Use this short test immediately: Closer to what?
Misconception 3: Shadow is a substance
What the learner may think. Dark material moves onto the screen.
Why it fails. A shadow is a region receiving less light. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Describe blocked light paths. Use this short test immediately: What reaches the screen?
Misconception 4: Only distance matters
What the learner may think. Orientation, source size and ambient light are irrelevant.
Why it fails. They affect outline, clarity or contrast. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Control them. Use this short test immediately: What else changed?
Misconception 5: A fuzzy edge has no size
What the learner may think. Blur makes measurement impossible.
Why it fails. A consistent boundary rule can still compare trials. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Define the measurement method first. Use this short test immediately: Where is the edge taken?
Misconception 6: More room light shrinks the shadow
What the learner may think. A lighter shadow is automatically smaller.
Why it fails. Brightness can change while geometric extent stays similar. The error feels efficient because it removes a decision, but it also removes the evidence boundary that makes the answer valid.
Targeted repair. Measure size and darkness separately. Use this short test immediately: Which dependent variable is requested?
Graded independent practice
Attempt each item without looking ahead. Write one line that identifies the controlling evidence before writing the final answer. Items 1–3 check recognition, 4–7 require explanation, and the later items change the surface form so that memory alone is insufficient.
Practice 1: Reference
Question. An object moves closer. What must be added to the statement?
Explained answer. State whether it moves closer to the lamp or the screen.
Why this answer earns trust. The two distances have different effects. Transfer variation: Draw both cases.
Practice 2: Near lamp
Question. Predict what happens when a card moves toward a nearby lamp while screen stays fixed.
Explained answer. Its shadow can enlarge.
Why this answer earns trust. The blocked boundary rays diverge over a longer path to the screen. Transfer variation: Keep orientation constant.
Practice 3: Near screen
Question. Predict what happens when the card moves toward the fixed screen.
Explained answer. Its shadow becomes smaller and closer to object size.
Why this answer earns trust. There is less post-object distance for ray separation. Transfer variation: Compare exact widths.
Practice 4: Fair test
Question. Name four constants in a distance investigation.
Explained answer. Lamp and setting, screen position, object and orientation, ambient light and measurement method.
Why this answer earns trust. Only one distance should vary. Transfer variation: Add fixed camera scale.
Practice 5: Observation
Question. A shadow becomes lighter after room lights turn on. Did its area necessarily shrink?
Explained answer. No. Contrast changed; area must be measured separately.
Why this answer earns trust. Brightness and size are different variables. Transfer variation: Propose two measurements.
Practice 6: Tilt
Question. Why can rotating the card invalidate the distance conclusion?
Explained answer. Its projected width changes with orientation.
Why this answer earns trust. Another plausible cause enters. Transfer variation: Use an angle guide.
Practice 7: Claim
Question. Repair: “The card grew when moved near the lamp.”
Explained answer. The card’s shadow enlarged on the screen while the card’s measured size remained unchanged.
Why this answer earns trust. The repair names the projection. Transfer variation: Add the changed distance.
Practice 8: Diagram
Question. Draw the two boundary rays for a card near the lamp.
Explained answer. Rays from the source touch opposite card edges and continue apart to the screen.
Why this answer earns trust. The construction shows magnification. Transfer variation: Repeat with card near screen.
Practice 9: Rule recall
Question. What controls shadow size in this setup?
Explained answer. Object size and orientation plus source-object-screen geometry; source size also affects edge clarity.
Why this answer earns trust. The shadow is relational. Transfer variation: Recall after two days.
Practice 10: Transfer
Question. Design a three-position test.
Explained answer. Use one marked rail, fixed lamp and screen, constant card angle, measured shadow width, repeated trials and a fixed camera scale.
Why this answer earns trust. The relationship is measurable and fair. Transfer variation: Predict the graph shape cautiously.
Delayed transfer: prove that the learning lasts
Transfer test 1: Ray-diagram set
Draw boundary rays for six object positions. Do this after a delay, without rereading the worked examples. The purpose is to test retrieval and decision-making, not immediate imitation.
Success criterion. Every diagram labels source, object, screen and both distances. If the criterion is not met, return to the smallest missing decision rather than repeating the entire chapter.
Transfer test 2: Delayed explanation
After one week, explain why the shadow changes without saying the object changes. Do this after a delay, without rereading the worked examples. The purpose is to test retrieval and decision-making, not immediate imitation.
Success criterion. The answer uses blocked diverging rays and fixed object dimensions. If the criterion is not met, return to the smallest missing decision rather than repeating the entire chapter.
Transfer test 3: Confound audit
Inspect apparatus drawings with moved screens, tilted cards or different bulbs. Do this after a delay, without rereading the worked examples. The purpose is to test retrieval and decision-making, not immediate imitation.
Success criterion. The learner names every extra variable before accepting a causal claim. If the criterion is not met, return to the smallest missing decision rather than repeating the entire chapter.
Examination control
1. Read the job before the story. Underline the command and the noun it governs. “Explain the change,” “state the word,” “find the fraction” and “identify the evidence” are different jobs even when the surrounding context is similar.
2. Separate given information from remembered information. Use only the facts supplied for the current task plus secure subject knowledge. Do not let a previous question, a familiar worksheet or an expected pattern silently become new evidence.
3. Write enough working to expose the decision. A marker or teacher should be able to see the relationship that justifies the answer. Extra sentences are not automatically stronger; the strongest working is concise, relevant and checkable.
4. Reserve a different-route check. For language, read the sentence for meaning and grammar. For mathematics, estimate or reverse the operation. For science, check the claim against the stated observation and a conservation or fair-test principle.
5. Stop when the requested job is complete. Unrequested speculation can contradict a correct answer. Add detail only when it explains the mechanism or satisfies another explicit part of the question.
Under time pressure, use a compact four-part margin routine: trigger → evidence → operation → check. Trigger names the feature that activates the method. Evidence identifies the exact words, values or observations allowed. Operation performs the language, mathematical or scientific step. Check asks whether the final statement answers the requested job, preserves units or referents, and avoids a stronger claim than the evidence supports.
A compact error log
After practice, do not record only “careless mistake.” Name the broken decision. Useful labels include trigger missed, evidence imported, relationship reversed, referent lost, unit dropped, operation correct but job wrong, and check repeated the same route. Add one prevention cue beside the label. A short accurate log is more useful than a long emotional account because it tells the learner what to do on the next item.
Review the log after two days and again after a week. Reattempt only one or two representative items first. If the method transfers, move to a mixed set. If it fails, repair the exact link between trigger and operation. This spacing matters because a solution can feel obvious while it is still visible and disappear when the page is closed.
Notes for parents and tutors
Use a cool, safe torch and card with adult supervision, keeping hot bulbs and electrical hazards away. The reasoning can also be practised entirely with diagrams.
Ask “closer to what?” every time a distance statement appears. This short question prevents the most common reversal.
Measure both card width and shadow width. The paired measurements make it concrete that a projection can change while the object remains the same.
The adult’s most useful question is not “Why were you careless?” but “Which decision did the evidence require?” Ask the learner to point to the controlling word, value, relationship or observation. If the learner can explain that link, reduce support. If the learner cannot, model one example and then change the surface details for the next attempt.
Frequently asked questions
Why can a shadow become larger?
Diverging boundary rays can spread farther between the object and the screen.
Does a larger shadow mean the object grew?
No. The object can remain the same size while the projection changes.
What happens when the object moves toward the screen?
Its shadow usually becomes smaller and closer to the object’s outline in a fixed lamp-screen setup.
Why can edges become fuzzy?
An extended light source creates overlapping full and partial-shadow regions.
What must a fair test keep constant?
Source, setting, screen, object orientation, ambient light and measurement method, apart from the chosen distance.
What is the safest conclusion?
State how measured shadow size changed under the named geometry while the object remained unchanged.
Next routes
Return to the complete volume directory to locate the series, use the original PSLE Learning Guide for the foundation route, and continue through PSLE Science for verified subject guidance. The next useful task is a mixed set in which this idea is sometimes relevant and sometimes irrelevant; that is the point at which a learner must choose, not merely copy.