lesson
An opaque object blocks light
1 · Learn
An opaque object blocks light from reaching part of a surface behind it, creating a shadow. The straight-line model explains why the outline relates to the object. The shadow depends on the object's orientation, the source and the screen, not just the object's name.
Moving an object nearer a small light source can make a larger shadow on a fixed screen. Change one distance at a time and record it; otherwise you cannot tell which change produced the result.
2 · Worked example
A circular card facing the source makes a round outline, while turning it edge-on changes the outline. The same object can therefore make different projected shapes.
3 · Your turn
Why should the source and screen stay fixed when testing how object position affects shadow size?
Check your answer
Keeping them fixed isolates the effect of object position rather than changing several distances at once.
4 · Apply your learning
Use a safe torch, card and screen with adult support; predict, measure and repeat at three labelled positions.
Adult guidance and safety
No Sun or laser experiments. Keep torch beams away from eyes and avoid a fully dark room with trip hazards.
Open your writing and drawing pad
Write, draw or show your working. Use a mouse, pen or finger. This pad is not a submitted answer.
Not saved to your account. Download your drawing as PNG and your typed notes as TXT before leaving or refreshing. They are separate files. Do not enter private information.
Open a picture saved on this device to draw on it again. Opening replaces the drawing, but Undo can restore it. PNG only, up to 4 MB and 4096 × 4096 pixels. The picture stays in this browser; it is not uploaded. Paper lines in a saved picture become part of that picture.
Clear the drawing? Your typed notes will stay. You can undo this action.
Your pad is empty.
Open a UTF-8 TXT file from this device, up to 40 KB and 10,000 characters. It stays in this browser. Opening can be undone until you type again. Downloads keep a new copy; they do not change the file you opened.
Replace the notes on this page with the opened file? Download the current notes first if you want to keep them.
Typed notes are not submitted answers.
Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
My observation notebook
With an adult, look at a safe real example or a checked photograph. Name the example and say which you used. Record what you actually notice. Do not taste plants or materials, approach unknown animals or invent missing observations.
Ask your teacher for support with the method and recording. A prediction is what you think might happen; an observation is what you actually see, hear or feel safely.
Keep your notebook: use Download notebook before leaving. Nothing is sent to the website or saved to your account. Reopen the downloaded notebook here to add another day's record. Do not include names, addresses or other private information.
Your records on this page
No observations recorded yet. Look first, then add one.
Reopening adds records; it does not replace your current records. Up to 50 records per notebook. Keep your downloads somewhere private. Editing this notebook does not submit work or complete a lesson.
Practice this lesson
Lesson resources
Browse the available practice activities and worksheets for this lesson.
Your progress