Electricity, Sound and Light

Chapter Ten: Light and Color 10.1 Properties of Light 10.2 Color and Vision 10.3 Optics

10.3 Basic optical devices Three useful optical devices are: 1.lenses 2.mirrors 3.prisms

10.3 Basic optical devices A magnifying glass is a converging lens. In survival situations, it can be used to make a hot spot. Mirrors can attract the attention of rescue teams from great distances.

10.3 Four ways light is affected by matter

All four interactions almost always happen together. A glass window is mostly transparent but also absorbs about 10% of light. The glass scatters some light (translucency) and reflects some light. Can you tell which colors are reflected and which are absorbed?

10.3 Light rays Reflection occurs when light bounces off a surface. Refraction occurs when light bends while crossing through materials.

10.3 Reflection There are two types of reflection; not all form images. A ray of light that strikes a shiny surface (like a mirror) creates a single reflected ray. This type of reflection is called specular reflection.

10.3 Reflection A surface that is dull, (or uneven) creates diffuse reflection. When you look at a diffuse reflecting surface you see the surface itself.

10.3 Refraction Materials with a higher index of refraction bend light by a large angle. The index of refraction for air is about Water has an index of refraction of 1.33.

10.3 Refraction Vegetable oil and glass have almost the same index of refraction. If you put a glass rod into a glass cup containing vegetable oil, the rod disappears because light is NOT refracted!

10.3 Lenses An ordinary lens is a polished, transparent disc, usually made of glass. For a converging lens, the first surface bends light rays toward the normal line. At the second surface, the rays bend away from the normal line and because of the curvature it bends toward the focal point.

10.3 Lenses The distance from the center of the lens to the focal point is the focal length. Light can go through a lens in either direction so there are always two focal points, one on either side of the lens.

Biology Connection Bioluminescence While there are only a few kinds of glowing creatures that live on land, about 90 percent of the animals that live in the deep parts of the ocean make their own light!

Activity Light travels in straight lines through tiny openings. When you aim the viewer at a brightly lit object, the object’s image will appear on the little screen in your viewer. Make a Pin Hole Viewer