Post on 05-Jan-2016
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