Properties of Light
Physical Science: Energy and Waves
Students examine how light travels in straight lines and behaves when it encounters different materials: reflection, refraction, and absorption. They use prisms to explore the visible spectrum and investigate color perception.
Learning Material
4 pagesHow Light Travels
How Light Travels#
Light is a form of electromagnetic energy that travels as a wave. Unlike sound, light dös not need a medium — it can travel through the vacuum of space, which is why we can see the sun and stars across billions of miles of empty space.
Light Travels in Straight Lines#
Light always travels in straight lines unless something bends or redirects it. We call these straight-line paths rays.
Evidence that light travels straight:
- Shadows — they have sharp edges because light cannot curve around objects
- A flashlight beam travels in a straight line
- Sunbeams streaming through a window are perfectly straight
Speed of Light#
Light travels at an incredible speed: approximately 300,000 kilometers per second (186,000 miles per second) in a vacuum. This is the fastest speed in the universe.
- Light from the sun takes about 8 minutes to reach Earth
- Light from the moon reaches us in about 1.3 seconds
- Light from the nearest star beyond our sun takes 4.2 years to reach Earth
Opaque, Translucent, and Transparent Materials#
Materials interact with light in different ways:
Transparent: Light passes through completely; you can see clearly through it.
- Examples: glass, clear water, air
Translucent: Light passes through partially; you can see shapes but not clearly.
- Examples: frosted glass, wax paper, thin fabric
Opaque: Light dös not pass through; you cannot see through it.
- Examples: wood, metal, your body
Shadows are formed when opaque objects block light. The shape of the shadow matches the outline of the object blocking the light.