Light and Shadows
Grade 3 · Science · Study Guide
Explore how light travels, reflects, and creates shadows.
Light is a form of energy that travels incredibly fast — about 186,000 miles per second! That's so fast that sunlight takes only about 8 minutes to travel the 93 million miles from the Sun to Earth. Light travels in straight lines, which is why we can't see around corners.
When light hits an object, one of three things can happen. If the object is transparent (like glass or water), light passes right through. If the object is translucent (like frosted glass), some light passes through but it gets scattered. If the object is opaque (like a wall or your hand), light cannot pass through at all — and that's what creates a shadow!
A shadow forms on the side of an object facing away from the light source. The size of a shadow depends on how close the object is to the light source and the angle of the light. Hold your hand close to a lamp — you get a big fuzzy shadow. Hold it farther away — the shadow is smaller and sharper.
Light can also be reflected (bounced off surfaces) or refracted (bent when passing from one material to another). A mirror reflects light very well, letting you see your own face. A prism refracts light and separates white light into all the colors of the rainbow — red, orange, yellow, green, blue, indigo, and violet.
Key terms
- transparent
- Allows light to pass through completely, like clear glass
- opaque
- Does not allow light to pass through; creates shadows
- shadow
- A dark area formed when an opaque object blocks light
- reflection
- Light bouncing off a surface
- refraction
- The bending of light as it moves from one material to another
Flashcards
- transparent
- Material that allows light to pass through completely
- opaque
- Material that blocks light completely, creating shadows
- translucent
- Material that allows some light through but scatters it
- shadow
- Dark area formed behind an opaque object blocking a light source
- reflection
- Light bouncing off a surface
- refraction
- Light bending as it passes from one medium to another
Practice questions
What kind of material creates a shadow by blocking light?
- Transparent
- Translucent
- Opaque
- Reflective
Show answer
Answer: Opaque
Opaque objects absorb or reflect all light, preventing any from passing through. This is what creates a shadow on the opposite side from the light source.
Light travels in curved lines.
Show answer
Answer: False
Light always travels in straight lines. This is why you can't see around a corner and why shadows have sharp edges.
When light bounces off a surface, it is called ___.
Show answer
Answer: reflection
Reflection occurs when light bounces off a surface. Mirrors are especially good reflectors, bouncing light at the same angle it arrives.
A prism separates white light into:
- Black and white only
- All colors of the rainbow
- Red and blue only
- Heat energy
Show answer
Answer: All colors of the rainbow
White light is actually made up of all colors mixed together. A prism bends (refracts) each color by a slightly different amount, splitting them into a visible spectrum.
Clear glass is an example of a transparent material.
Show answer
Answer: True
Clear glass, clean water, and clear plastic wrap are all transparent — light passes through them with little disturbance, so you can see clearly through them.
Fun facts
- A solar eclipse happens when the Moon's shadow falls on Earth — it's the Moon blocking sunlight from reaching part of our planet!
- You actually see objects because light bounces off them and into your eyes, not because your eyes send out light.
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