Use the Patterns of Light submodules on Light and Optics to learn about Light, Lenses, Color, and Optics in Nature (four submodules) and answer these questions.

• What is the difference between refraction and reflection?
• Which object refracts--a lens or a mirror? Which reflects?
• What is meant by the focal length of the lens? How can it be measured?
• What happens light passes through an interface between different media, such as glass and air?
• What happens to the speed of light when it goes from air into glass?
• What is the refractive index of a medium?
• A transparent blob of goo has a large refractive index (3). What does this imply about the speed of light in the goo?
• What is the difference between a real image and a virtual image.
• What is the difference between a concave and a convex lens? How does each refract light?
• Lens A has a negative focal length: where is its focal point?
• Lens B has a positive focal length: where is its focal point?
• Which mirrors can create a real image, a convex mirror or a concave mirror? Why? (Look at both sides of a large spoon and see!)
• Why do you only need 2-3 "rays" to show how the light going through a lens will bend?

Things to learn from rainbows (Optics in Nature)

• Which color reflects more, red, blue, or green?
• How does the air act like a lens?
• How does a raindrop disperse and reflect light, acting like both a prism and a mirror?
• What is the antisolar point? Why do we want to know where it is in order to look for a rainbow?
• Do you see the same rainbow as your friend who is a few feet away from you?
• Why do secondary rainbows occur?