Light and Color 4 th Grade Science

Core Content Unifying Concepts SC Students will: analyze models/representations of light in order to generalize about the behavior of light. represent the path of light as it interacts with a variety of surfaces (reflecting, refracting, absorbing). Light can be observed as traveling in a straight line until it strikes an object. Light can be reflected by a shiny object (e.g., mirror, spoon), refracted by a lens (e.g., magnifying glass, eyeglasses) or absorbed by an object (e.g., dark surface). Questions posed about the behavior and interaction of light with a variety of surfaces, can be explored through investigations using simple equipment.

Essential Question What does color have to do with light? What makes a rainbow?

Vocabulary Prism – a solid object that bends (refracts) light. Visible spectrum – The range of light energy that people can see –Remember ROY G BIV –Red, orange, yellow, green, blue, indigo, and violet

Real Life Application Have you ever seen a rainbow? Have you ever wondered what causes a rainbow?

Facts about Light What color is the sun? Actually, sunlight is a mixture of all the colors of the rainbow. –White is the color of all the sun’s colors mixed together. Different colors of light travel at different speeds in water and in glass. –So when white light moves from air to glass or from air to water, the different colors of light bend at different angles and separate into each individual color.

Prisms A prism is a solid object that bends light. –When white light hits a prism, each color of light bends at a different angle. –Red light is bent the least. –Blue light is bent the most. –The light that passes through a prism separates into a rainbow.

Visible Spectrum The visible spectrum is made up of all the colors of light that people can see. –These colors are red, orange, yellow, green, blue, indigo, and violet.

Rainbows You can sometimes see a rainbow in the sky during a summer rain when the sun is out. Because of the way the raindrops refract and reflect white sunlight, you can see a rainbow only when the sun is behind you.

Rainbows Cont’d Each drop of falling water in a rainstorm is like a tiny prism and mirror. Sunlight enters a drop, is reflected from the back wall, and then passes out through the front. So, it is refracted twice just as it is in a prism.

Rainbows Cont’d There are more colors in a rainbow than anyone could count, however, most people use just seven to remember the order in which the bands always appear: red, orange, yellow, green, blue, indigo, and violet.

Adding Colors A prism breaks white light into colors. You can also add colors together. When you add different colored lights together, they form other colors. –Shining a red light and a green light onto the same spot will make a yellow light. –Shining a blue light and a red light onto the same spot will make a purple light. –You can add red light, blue light, and green light in different ways to make all other colors.

Adding Colors

Televisions and computer monitors add light colors. –The inside of a TV screen is coated with millions of tiny dots of red, green, and blue. –Dots that are near each other are made to glow in different patterns and brightnesses. –Your eyes combine the colors to make the pictures you see.

Seeing Colors All the colors of light, called white light, hit every object you see. Most objects absorb most of the light, but not all of it.

Seeing Colors Cont’d What colors are being absorbed and reflected in the following pictures?

Seeing Colors Cont’d

Mixing paint colors is a way of controlling absorption and reflection. –Yellow paint reflects yellows and absorbs other colors. –Blue paint reflects blues and absorbs other colors. When you mix yellow and blue, all the other colors are absorbed except greens. –So, you see shades of green when you mix blue and yellow paint. When you mix all paint colors, almost all light is absorbed, so you see black.

Ticket Out the Door 1.Describe how a prism works. 2.Name the colors that make up white light. 3.Which light colors are absorbed and which are reflected by a yellow tulip?

Let’s Review White light is made up of many colors mixed together. A prism separates the colors. Raindrops act like prisms to form rainbows. You can make colors by adding different colored lights. The colors of objects you see are the oclors of light that the objects reflect.