Exploring Light and Its Properties in Georgia's Performance Standards

1. LIGHT

2. Georgia Performance Standards S4P1 Students will investigate the nature of light using tools such as mirrors, kenses, 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.

3. 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?

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

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

6. 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.

7. 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 bounces off of them.

8. 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.

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

10. TRANSPARENT • Some kinds of matter, such as air and glass, are 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.

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

12. 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.

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

14. STOP HERE!

15. Properties of Light • Reflect • Refract • Absorb

16. What is reflection? • Most of the light that reaches us is reflected light. • Reflection occurs when light strikes a surface and bounces off. • The law of reflection says that the incoming angle of light is equal to the outgoing angle of reflection.

17. Reflected Images

18. What is refraction? • Refraction is the bending of light as it passes from one material into another. • Here light is traveling through air and water. Light slows down as it travels through water because water is more dense.

19. Refraction (Cont.) www.jnvkannur.temple.at

20. Tools that refract light • Lenses are tools that refract light. • They are used to gather light rays or spread them apart. • You use them in glasses, cameras, microscopes, flashlights, and telescopes. • There are two types of lenses – convex and concave.

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

22. Convex lenses • Convex lens bulge in the middle. • A convex lens brings rays of light together. • Examples of a convex lens are a magnifying glass, microscopes, and telescopes. • X marks the spot!

23. CONCAVE LENS • A concave lens bends light rays outward.

24. Concave lenses • A concave lens curves inward. • A concave lens spreads light apart. • Examples of a concave lens are found in a flashlight and car headlights. • You use concave lenses while exploring in a cave.

25. 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.

26. How do we see? • Light travels in through our cornea to an opening – pupil (black spot). • It is focused by our lens to the back of our eye – retina. • These images are upside down. • The optic nerve takes the images to the brain where it sees the image right-side up!

27. Correcting vision with lenses • When light passes through a lens, it will bend toward the thickest part. • A nearsighted person’s lens focuses incoming light in front of the retina. • A concave lens corrects nearsighted vision by spreading light out before it enters the eye so it focuses in the correct spot. • A farsighted person’s lens focuses incoming light in back of the retina. • A convex lens corrects farsighted vision by bringing light together before it enters the eye so it focuses in the correct spot.

28. THE EYE

29. How do you see colors? • If white light is shining on a green leaf, how do we see green? • The leaf absorbs all of the colors of the visible spectrum except green and reflects green off and into your eyes. • If there is no light, you cannot see colors.

30. Black and white? • Black and white are not true colors. • White things appear white because they reflect all wavelengths of light. • White objects do not absorb any light energy. • They tend to be cooler. • We wear white in the summer to stay cool.

31. Black is black • Black objects do the opposite. • They absorb all the light. • They tend to be warmer when placed in sunlight. • We wear black and dark colors in the cold.

32. 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.

33. PRISM

34. 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.

35. 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. Red Orange Yellow Green Blue Indigo Violet

36. Light • All light is made of transverse waves. • Light can be described using wavelengths. • A wavelengthis the distance from the top of one wave to the top of the next wave. • Red has the longest wavelength while violet has the shortest.

37. 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

38. 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.

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

40. 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.

41. 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.

42. 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?