Light

1. Light Have you ever seen a rainbow in the sky? Rainbows are made of light. How do they form? Why do they have different colors?

2. Prism • An object that separates white light into bands of colored light. • Isaac Newton was the first to show that white light is made of all the colors we can see.

3. Wavelengths and Waves • Like sound, light travels in waves. • Light waves have different wavelengths. • The longer the wavelength, the less energy it has.

4. How does light travel? • Refraction – the bending of light as it passes from one material into another. • Lenses – a tool that refracts light. • Concave – curves inward. • Glasses that help you see faraway objects are made with concave lenses. • Convex – bulges outward. • Reading glasses have convex lenses.

5. The Human Eye • Light passes through a thin, clear tissue covering each eye (cornea). • The light passes through an opening in the eye (pupil). • Light moves through a lens at the front of the eye. • The lens refracts the light from the image and focuses the image onto the back of the eye (retina). • The retina changes that image into signals and the optic nerve sends these signals to the brain.

6. What is reflection? • Reflection – the way a light wave hits a surface and bounces off. • Smooth, shiny surfaces reflect almost all of light. • Dull, rough surfaces reflect the least amount of light. • Liquid and gas surfaces can also reflect light. • The color of an object depends on the colors it reflects.

7. How mirrors work • Convex mirrors spread out the reflected light rays. • Convex mirrors are used as rearview mirrors in vehicles. • Concave mirrors focus the reflected light rays together at a point.

8. What can light pass through? • Transparent – allows light to pass through. • Light travels in a straight line through pure air, water, and empty spaces. • Translucent – scatters light in different directions. • Some shower doors are made of translucent plastic. • Opaque – blocks light completely. • Wood and metal are opaque.