1. How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show”, or simply press F5 on the top row of your keyboard. To advance to the next slide click the left mouse button once. From the Chapter screen you can click on any section to go directly to that section’s presentation. Blank or “missing” areas of a slide will remain hidden until the left mouse button is clicked. You may exit the slide show at any time by pressing the Esc key Copyright © by Holt, Rinehart and Winston. All rights reserved.

2. The Nature of Light Module O: Chapter 3 Section 1: What Is Light? Section 2: The Electromagnetic Spectrum Section 3: Interactions of Light Waves Section 4: Light and Color Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

3. What Is Light? Section 1 Bellringer Some of the following questions have been debated for centuries. Record your responses to them in your science journal. What do you think light is? Is light made of matter, or is it purely energy? What is your reason for your answer? Can light travel through space? Copyright © by Holt, Rinehart and Winston. All rights reserved.

4. What Is Light? Section 1 Objectives Describe light as an electromagnetic wave. Calculate distances traveled by light by using the speed of light. Explain why light from the sun is important. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

5. What Is Light? Section 1 Light: An Electromagnetic Wave Electric and Magnetic Fields An electric field surrounds every charged object. A magnetic field surrounds every magnet. How EM Waves Are Produced An electromagnetic wave, shown on the next slide, can also simply be called an EM wave. An EM wave can be produced by the vibration of an electrically charged particle. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

6. An Electromagnetic Wave Section 1 Copyright © by Holt, Rinehart and Winston. All rights reserved.

7. What Is Light? Section 1 The Speed of Light Warp Speed In the near vacuum of space, the speed of light is about 300,000,000 m/s, or 300,000 km/s. Copyright © by Holt, Rinehart and Winston. All rights reserved. An Eight Minute Delay Even though light travels quickly, it takes about 8.3 min for light to travel from the sun to Earth. It takes this much time because Earth is 150,000,000 km away from the sun. Light from the Sun End of Slide

8. The Electromagnetic Spectrum Section 2 Bellringer What are the weather conditions necessary to see a rainbow? Why do rainbows form? When else can you see a rainbow-like phenomenon? Record your answers in you science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

9. The Electromagnetic Spectrum Section 2 Objectives Identify how electromagnetic waves differ from each other. Describe some uses for radio waves and microwaves. List examples of how infrared waves and visible light are important in your life. Explain how ultraviolet light, X rays, and gamma rays can be both helpful and harmful. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

10. The Electromagnetic Spectrum Section 2 Characteristics of EM Waves Copyright © by Holt, Rinehart and Winston. All rights reserved. Same Speed, Different Frequency All EM waves travel at the same speed in a vacuum. The Electromagnetic Spectrum The entire range of EM waves is called the electromagnetic spectrum. The electromagnetic spectrum is shown on the next slide. End of Slide

11. The Electromagnetic Spectrum Section 2 Copyright © by Holt, Rinehart and Winston. All rights reserved.

12. The Electromagnetic Spectrum Section 2 Radio Waves Broadcasting Radio Signals Radio stations encode sound information into radio waves by varying either the waves’ amplitude or their frequency. Comparing AM and FM Radio Waves AM radio waves have longer wavelengths than FM radio waves do. And AM radio waves can bounce off the atmosphere and thus can travel farther than FM radio waves. But FM radio waves are less affected by electrical noise than AM radio waves are. Radio Waves and Television Like radio signals, television signals are broadcast using amplitude modulation and frequency modulation. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

13. The Electromagnetic Spectrum Section 2 Microwaves Microwaves and Communication Like radio waves, microwaves are used to send information over long distances. For example, cellular phones send and receive signals using microwaves. Radar Microwaves are also used in radar. Radar (radio detection and ranging) is used to detect the speed and location of objects. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

14. The Electromagnetic Spectrum Section 2 Infrared Waves Shorter Wavelengths, Higher Frequencies Infrared waves have shorter wavelengths and higher frequencies than microwaves do. Almost all things give off infrared waves, including buildings, trees, and you! The amount of infrared waves an object gives off depends on the object’s temperature. Warmer objects give off more infrared waves than cooler objects do. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

15. The Electromagnetic Spectrum Section 2 Visible Light Visible Light from the Sun Some of the energy that reaches Earth from the sun is visible light. The visible light from the sun is white light. White light is visible light of all wavelengths combined. Colors of Light Humans see the different wavelengths of visible light as different colors. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

16. The Electromagnetic Spectrum Section 2 Ultraviolet Light Bad Effects Too much ultraviolet light can cause skin cancer, wrinkles, and damage to the eyes. Good Effects On the good side, ultraviolet waves produced by ultraviolet lamps are used to kill bacteria on food and surgical tools. In addition, small amounts of ultraviolet light are beneficial to your body. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

17. The Electromagnetic Spectrum Section 2 X Rays and Gamma Rays X Rays X rays have wavelengths between 0.001 nm and 60 nm. They can pass through many materials. This characteristic makes X rays useful for medicine and security. Gamma Rays Gamma rays are EM waves that have wavelengths shorter than 0.1 nm. They can penetrate most materials very easily.Gamma rays are used to treat some forms of cancer. Gamma rays are also used to kill harmful bacteria in foods, such as meat and fresh fruits. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

18. Interactions of Light Waves Section 3 Bellringer Mirrors are common objects that most people use every day. From your experience, explain how mirrors work and describe what they do to light waves. Record your responses, including any illustrations you might want to use, in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved.

19. Interactions of Light Waves Section 3 Objectives Describe how reflection allows you to see things. Describe absorption and scattering. Explain how refraction can create optical illusions and separate white light into colors. Explain the relationship between diffraction and wavelength. Compare constructive and destructive interference of light. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

20. Interactions of Light Waves Section 3 Reflection Copyright © by Holt, Rinehart and Winston. All rights reserved. The Law of Reflection The law of reflection states that the angle of incidence is equal to the angle of reflection. This law is illustrated on the next slide. Types of Reflection Regular reflection and diffuse reflection are illustrated on the next slide. Light Source or Reflection? You can see a light source even in the dark because its light passes directly into your eyes. Most things around you are not light sources. But you can still see them because light from light sources reflects off the objects and then travels to your eyes. End of Slide

21. Law of Reflection Section 3 Copyright © by Holt, Rinehart and Winston. All rights reserved.

22. Interactions of Light Waves Section 3 Absorption and Scattering Copyright © by Holt, Rinehart and Winston. All rights reserved. Absorption of Light The transfer of energy carried by light waves to particles of matter is called absorption. Scattering of Light Scattering is an interaction of light with matter that causes light to change direction. End of Slide

23. Interactions of Light Waves Section 3 Refraction Copyright © by Holt, Rinehart and Winston. All rights reserved. Refraction and Material Refraction is the bending of a wave as it passes at an angle from one substance, or material, to another. Refraction and Optical Illusions Your brain always interprets light as traveling in straight lines. But when you look at an object that is underwater, the light reflecting off the object refracts. Refraction and Color Separation White light can be separated into different colors during refraction. End of Slide

24. Interactions of Light Waves Section 3 Diffraction Copyright © by Holt, Rinehart and Winston. All rights reserved. What Is Diffraction? Diffraction is the bending of waves around barriers or through openings. Diffraction and Wavelength The wavelength of visible light is very small—about 100 times thinner than a human hair! So, a light wave cannot bend very much by diffraction unless it passes through a narrow opening, around sharp edges, or around a small barrier. End of Slide

25. Interactions of Light Waves Section 3 Interference Copyright © by Holt, Rinehart and Winston. All rights reserved. Constructive Interference When waves combine by constructive interference, the resulting wave has a greater amplitude, or height, than the individual waves had. Destructive Interference When waves combine by destructive interference, the resulting wave has a smaller amplitude than the individual waves had. End of Slide

26. Light and Color Section 4 Bellringer What is your favorite color? In a short paragraph in your science journal, explain why you like your favorite color. What color do you associate with anger? with happiness? with death? How do certain colors affect your mood? Copyright © by Holt, Rinehart and Winston. All rights reserved.

27. Light and Color Section 4 Objectives Copyright © by Holt, Rinehart and Winston. All rights reserved. Name and describe the three ways light interacts with matter. Explain how the color of an object is determined. Explain why mixing colors of light is called color addition. Describe why mixing colors of pigments is called color subtraction. End of Slide

28. Light and Color Section 4 Light and Matter Copyright © by Holt, Rinehart and Winston. All rights reserved. The Passage of Light Transmission is the passing of light through matter. Types of Matter Matter through which visible light is easily transmitted is said to be transparent. Translucent matter transmits light but also scatters the light as it passes through the matter. Matter that does not transmit any light is said to be opaque. End of Slide

29. Light and Color Section 4 Colors of Objects Colors of Opaque Objects When white light strikes a colored opaque object, some colors of light are absorbed, and some are reflected. Only the light that is reflected reaches your eyes and is detected. So, the colors of light that are reflected by an opaque object determine the color you see. Colors of Transparent and Translucent Objects When you look through colored transparent or translucent objects, you see the color of light that was transmitted through the material. The other colors were absorbed. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

30. Light and Color Section 4 Mixing Colors of Light Color Addition When colors of light combine, you see different colors. Combining colors of light is called color addition. Color addition is illustrated on the next slide. Light and Color Television The colors on a color television are produced by color addition of the primary colors of light. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

31. Color Addition Section 4 Copyright © by Holt, Rinehart and Winston. All rights reserved.

32. Light and Color Section 4 Mixing Colors of Pigment Pigments and Color A pigment is a material that gives a substance its color by absorbing some colors of light and reflecting others. Color Subtraction When you mix pigments together, more colors of light are absorbed or taken away. So, mixing pigments is called color subtraction. Copyright © by Holt, Rinehart and Winston. All rights reserved. End of Slide

33. The Nature of Light Chapter 22 Concept Map Copyright © by Holt, Rinehart and Winston. All rights reserved. Use the following terms to complete the concept map on the next slide: magnetic fields, electromagnetic waves, reflections, electric fields, light, absorption transmission.

34. Concept Map Chapter 22 Copyright © by Holt, Rinehart and Winston. All rights reserved.

35. Concept Map Chapter 22 Copyright © by Holt, Rinehart and Winston. All rights reserved.