Watch this shadow on the wall. When the torch creeps up or down, the dark shape stretches and shrinks. What do you think makes it longer or shorter?
A shadow is the dark shape you get when something blocks light. Opaque means light cannot go through it, so a wooden block is opaque and makes a clear shadow.
Light height is how high we hold the torch above the table. That is the one thing we will change today.
A fair test means we change only one thing, measure one thing, and keep everything else the same. If we keep the object still and only move the torch higher or lower, what do you think will happen to the shadow?
On the screen you will see a lamp, an object and the shadow it casts. Watch what happens to the shadow when the lamp moves higher or lower. Predict first: will the shadow get longer or shorter when the lamp is low?
Why does the shadow change?
Our question: does torch height change how long a shadow is? Take each card on the board in turn and call out the bin it belongs in (Change, Measure, or Keep the same) and say why you put it there.
Then, as a group, choose the three torch heights you will test (for example 10 cm, 20 cm and 30 cm above the table, or three clear heights of your own). Write those heights on your Investigation Journal page so you are ready for the test. Then finish the I predict... because... line: as the torch goes higher, will the shadow get longer or shorter, and why?
Does torch height change shadow length?
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