LIGHT

Georgia Performance Standards S4P1 Students will investigate the nature of light using tools such as mirrors, lenses, and prisms. Identify materials that are transparent, opaque, and translucent. Investigate the reflection of light using a mirror and a light source. Identify the physical attributes of a convex lens, a concave lens, and a prism and where each is used.

ESSENTIAL QUESTIONS What are the characteristics of light and how does it normally behave? How can we describe the movement of light as it passes through different substances? How do lenses bend light in specific ways in order to accomplish useful jobs?

LIGHT You are able to see objects when the light traveling from them enters the eye. Shadows form when light is blocked.

LIGHT Light is a form of energy that you can see. Energy is the ability to cause change. Light and sound are forms of energy that travel in waves. Light waves travel in straight lines in every direction away from their source.

LIGHT WAVES Light waves can travel through certain kinds of matter, such as air or clear glass. Light can also travel empty space. This is how light from the Sun reaches the Earth and other planets.

LIGHT A few things, such as a lamp or fireflies, can give off their own light. MOST things do not do this. You can see objects because the light from other sources bounce off of them.

LIGHT Light reacts in different ways when it meets different kinds of matter. We can see through water and glass, but we cannot see through things like walls, metal, or rock.

OPAQUE Materials such as wood, metal, and rock all block light waves. The are known as OPAQUE. An opaque material blocks light from passing through it.

TRANSPARENT Some kinds of matter, such as air and glass, are called TRANSPARENT. A transparent material allows light to pass through it. Think about a picture in a picture frame. You can still see the picture even though it has a piece of glass in front of it.

TRANSLUCENT Certain materials are TRANSLUCENT. A translucent material allows some light to pass though it and scatters the light in many directions. Frosted glass is translucent. Objects seen through translucent objects appear blurry.

SHADOWS Light waves travel in straight lines from their source. If you stand in front of the sunlight, some of the light waves will strike your body. Your body will block some of the waves. The other light waves will go around your body until it reaches an opaque object such as the ground.

SHADOWS The part of your body that is blocking the light waves will create a shadow.

How does light travel? Light waves REFLECT, or bounce, off the surfaces of most objects.

REFRACTION Light waves REFRACT when they move from one transparent material to another, such as from air to glass or to water. TO REFRACT IS TO BEND.

LENS People put refraction to good use by making lenses. A lens is a piece of curved glass, plastic, or other metal that refracts light.

CONCAVE LENS A concave lens bends light rays outward.

CONVEX LENS A convex lens bends light waves inward towards a focal point.

THE EYE The eye is a very special sense organ. It contains parts that focus light and control the amount of light that enters. Cells in the back of the eye receive the light and send messages to the brain.

THE EYE

COLOR When light strikes an object, the color of the light affects the way the object is seen. WHITE LIGHT is actually a collection of light waves of different colors. A PRISM is a piece of glass or other transparent material that separates white light into colors.

PRISM

A triangle shaped piece of glass can act as a prism A triangle shaped piece of glass can act as a prism. So can tiny water droplets that hang in the air after a rainfall. This is why you can see a rainbow in the sky.

Notice that the colored bands in a prism are always arranged in the same order. This happens because the prism bends each color at a specific angle. ROY G. BIV Red Orange Yellow Green Blue Indigo Violet

A good way to remember the order of the colors is to remember the name ROY G BIV. R= red O= orange Y= yellow G= green B= blue I = indigo V= violet

Isaac Newton In 1965, he passed the colored bands into a second prism which caused them to be combined into white light. This proved that sunlight is made of colored parts.

SEEING COLORS Most objects will ABSORB, or take in, some of the light that strikes their surface. A colored object absorbs some colors of light but reflects other colors. You see only the reflected colors.

SEEING COLORS A banana looks yellow because it reflects yellow light. The other colors in the spectrum are absorbed by the banana.

COLORED LIGHT A color of an object depends on the color of light it reflects. It also depends on the color of light shining on it. Remember that WHITE LIGHT is made up of all the colors of the rainbow.

WHAT WOULD HAPPEN IF YOU SHINED A RED LIGHT ON A WHITE SNEAKER? When a red colored light shines on a white shoe, the shoe will reflect the color of that light. The shoe will look red. When a green light shines on a white object, that object will look green.

ESSENTIAL QUESTIONS What are the characteristics of light and how does it normally behave? How can we describe the movement of light as it passes through different substances? How do lenses bend light in specific ways in order to accomplish useful jobs?