Behavior of Light

Getting the Idea

• Light is another form of energy.

• You can see all the objects around you because the sun (or a lamp) is sending out light energy.

• Light travels in the form of waves.

• Light waves behave in predictable ways.

Light Waves

• Light waves move in a straight path called a ray.

• You can see a light’s straight path when you use a flashlight.

• When light strikes an object, it either passes through the object or is blocked by the object; depending on what the object is made of.

• Light passes easily through transparent materials, such as clear glass and pure water.

• These materials transmit light or allow its passage.

• Translucent materials, such as wax paper, scatter the light that they transmit. You cannot see clearly through translucent materials.

• Opaque materials, such as wood and metal, block light completely. You cannot see at all through opaque materials

Lenses

• A lens is a clear material that has at least one curved surface.

• When light strikes a lens, its path changes – it bends.

• Lenses are shaped so that light that enters them bends and refocuses in a way that helps people see better. They are also used in microscopes, telescopes, and cameras.

• A convex lens is thicker in the middle than at its edges. Light that enters a convex lens is bent inward. The light bends toward a point called the focus.

• A concave lens has thicker edges and a thinner middle. Light that enters a concave lens is bent outward.

Refraction

• The bending of light is called refraction. Clear plastic, glass, and water all refract light.

Absorption and Reflection• Only materials that transmit

light can refract it. • Other materials affect the

path of light waves in different ways. Some materials change light energy into heat energy. This process is called absorption.

• The bouncing of light off a surface is called reflection.

• Everything we see reflects some light.

Test…Ready booklet

• #12, p. 6• #4, p. 15• # 16, p. 24• Light sources and light rays -• http://www.engineeringinteract.org/resources/

alienattack/flash/concepts/sourcesandrays.htm• Reflection: seeing objects –• http://www.engineeringinteract.org/resources/

alienattack/flash/concepts/reflectionseeingobjects.htm