1. Chapter 9: Waves and Light

2. Lesson 1: Waves of the Electromagnetic Spectrum Key Questions: – 1. How does the Sun’s energy arrive on Earth? – 2. How do Electromagnetic Waves compare? – 3. What makes up the Electromagnetic Spectrum? Sunshine Standards: – SC.7.9.10.1: Illustrate that the sun’s energy arrives as radiation with a wide range of wavelengths, including infrared, visible, and ultraviolet, and that white light is made up of a spectrum of many different colors.

3. How does the Sun’s energy arrive on Earth? As you sit in class taking notes you are surrounded by waves from the sun you cannot see or hear There are many different types of there waves: Infrared rays, visible light, Ultraviolet rays, and a few other types! These waves are all electromagnetic waves.

4. Characteristics of Electromagnetic Waves An electromagnetic wave is a disturbance that involves the transfer of electric and magnetic energy. An electromagnetic wave is made up of vibrating electric and magnetic fields that more through space or some medium at the speed of light.

5. Characteristics of Electromagnetic Waves An electromagnetic wave can begin with the movement of charged particles, all of which have electric fields around them. As the particles change speed or direction, a vibrating electric field is created.

6. Electric and magnetic fields produce each other repeatedly, the result is an electromagnetic wave.

7. Energy The energy that electromagnetic waves transfer through matter or space is called electromagnetic radiation. Electromagnetic waves do not require a medium such as air, so they can transfer energy through empty space. The sun’s energy arrives on Earth as electromagnetic radiation.

8. How do electromagnetic waves compare? Light, radio waves, and x-rays are all electromagnetic waves, but each has properties that make it more useful for some purposes than others.

9. The distance between the crest of one wave and the crest of the next wave is called the wavelength.

10. The frequency of a wave is the number of waves that pass a given point in a certain amount of time.

11. All electromagnetic waves travel the same speed in a vacuum, but they have different wavelengths and different frequencies. A vacuum is a space that contains no air or other gas.

12. Different Types of Waves and How they Compare Visible Light is the only range of wavelengths your eyes you can see. Your radio detects radio waves, which have much longer wavelengths than visible light. X-rays, on the other hand, have much shorter wavelengths than visible light.

13. Wavelengths and Frequency As wavelength decreases, frequency increases. Waves with the longest wavelengths have the lowest frequencies. Waves with the shortest wavelengths, have the highest frequencies. The higher the frequency of the wave, the higher its energy.

15. Spectrograph A device called a spectrograph can be used to show that the sun’s radiation includes all of these different types of waves.

16. What makes up the electromagnetic spectrum? The complete range of electromagnetic waves placed in order of increasing frequency is called the electromagnetic spectrum. The electromagnetic spectrum is made up of radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.

17. Radio Waves Electromagnetic waves with the longest wavelengths and the lowest frequencies are radio waves. Radio Waves are used in broadcasting to carry signals for radio programs.

18. Radio Waves Broadcast stations sends out radio waves at certain frequencies, and your radio picks up these waves and turns it into an electrical signal.

19. Microwaves Microwaves have shorter wavelengths and higher frequencies than radio waves do. When you think about microwaves you probably think about microwave ovens, but they also used for cellular phone communication and radar.

20. Infrared Rays The heat from your stove is infrared radiation or infrared rays. Infrared Rays are electromagnetic waves with wavelengths shorter than a microwave. They have higher frequencies and therefore more energy than microwaves.

21. Infrared Rays These ways are often called heat rays because you can feel the energy of infrared rays as heat. Example: heat lamps have bulbs that give off mainly infrared rays, and they are used to keep things warm. Things like food in the cafeteria and young animals in an incubator.

22. Infrared Cameras Warmer objects give off more infrared rays than cooler objects. Infrared cameras use infrared rays instead of visible light to take pictures called thermograms. These pictures are an image that shows regions of different temperatures in different colors.

23. Visible Light Electromagnetic waves that you see are called visible light. The make up only a small part of the electromagnetic spectrum. Visible light waves have shorter wavelengths and higher frequencies than infrared rays.

24. Visible Light Visible light that appears white is actually a mixture of many colors. Recall that light waves bend, or refract, when they enter a new medium. For example, when white light passes through rain droplets, a rainbow can result.

25. Ultraviolet Rays These are electromagnetic waves with wavelengths just shorter than those of visible light. Ultraviolet rays have higher frequencies than visible light, so they carry more energy. The energy from these rays can damage or kill living cells.

26. X-Rays These are electromagnetic waves with wavelengths just shorter than those of ultraviolet rays. Their frequencies are just a little higher than ultraviolet rays. Because of their high frequencies x-rays can penetrate most matter.

27. X-Rays However, dense matter like bone or lead, absorbs x-rays and they do not pass through. That’s why we use them to take pictures of our bones and teeth. Too much exposure can lead to cancer.

28. Gamma Rays Electromagnetic waves with the shortest wavelengths and highest frequencies are gamma rays. Because these rays have the greatest amount of energy, they are the most penetrating.

29. Gamma Rays Because they are the most penetrating we can examine the body’s internal structure. A patient is injected with a fluid that emits gamma rays, then a gamma ray detector can take pictures of the internal structures.

30. Gamma Rays Certain radioactive substances and certain nuclear reactions produce gamma rays. Astronomers also think distant exploding stars produce gamma rays.