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Grade 4 (age 9-10)

Shadows and Mirrors

Shadows and Mirrors

Light travels in straight lines, so an opaque object casts a dark shadow behind it. The closer the light, the bigger the shadow; moving it away shrinks it again. A mirror bounces light back, and the angle in always matches the angle out, so you slide the light to grow shadows and reflect rays.

Why do shadows form?
30
🌗 For a shadow to form?
①There must be light
②An object must block the light
③If light cannot pass, a dark shadow forms behind
④Closer light → bigger shadow
⑤Farther light → smaller shadow
Mirrors bounce light
30
🪞 Mirror Reflection
①Light bounces off mirrors
②Incoming angle = outgoing angle
③This is the law of reflection
④You see your image because of reflection
Summary
Shadow Condition
Light + opaque object → Shadow
Blocking light creates a dark shadow behind
Law of Reflection
Incident angle = Reflection angle
Light bounces off a mirror at the same angle it arrives
🎯 Key Points
①Light travels in straight lines
②Shadows form behind opaque objects
③Closer light = bigger shadow
④Mirrors reflect at equal angles
⑤Transparent objects make faint shadows
Examples and Unit Test
Example 1
If you move a flashlight closer to an object, what happens to the size of the shadow?
1
A shadow forms behind an object when light is blocked by the opaque object.
2
The closer the light source is to the object, the larger the shadow becomes.
▸ The shadow becomes larger
A closer light source makes a larger shadow; a farther one makes it smaller.
Example 2
Light hits a mirror at a slant of 30 degrees. What is the angle of reflection?
1
When light hits a mirror, it bounces off at the same angle it came in (law of reflection).
2
Since the angle of incidence is 30 degrees, the angle of reflection is also 30 degrees.
▸ 30 degrees (incidence = reflection)
In a mirror reflection, the angle of incidence equals the angle of reflection.
Unit-test style
Which statement about shadows and mirrors is correct?
①Light curves as it travels, which makes shadows
②In a mirror, the angle of incidence equals the angle of reflection
③A shadow gets larger as the light source moves away
④Clear glass makes a dark shadow
⑤A mirror absorbs all the light
▸ ② In a mirror, the angle of incidence equals the angle of reflection
1
Light bounces off a mirror at the same angle it came in, so incidence equals reflection.
2
Light travels straight and makes shadows (①), a closer light source makes a larger shadow (③), clear objects let light through so their shadow is faint (④), and a mirror reflects light (⑤).
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