1. Electromagnetic Waves and the Electromagnetic Spectrum Unit 32

4. Which of the following is NOT an example of an electromagnetic wave? A. X-ray B. Microwave C. Visible light D. Sound wave

5. Which of the following is NOT an example of an electromagnetic wave? A. X-ray B. Microwave C. Visible light D. Sound wave

6. Behavior and Color of Light Interactions of Light When light strikes a new medium or substance, the light can be reflected, absorbed, or transmitted. When light is transmitted it can be refracted, polarized, or scattered.

7. Scattering and Refraction Why is the sky blue?

9. It is due to the scattering of the light rays (REFRACTION).

10. The sunlight gets scattered by the molecules of the atmosphere.

12. Sunset in our Atmosphere Larger particles like dust and water droplets reflect red light causing dusk and dawn to look red and orange.

13. Refraction Refraction is the bending of light that is caused by a change in speed when the light wave goes from one medium into another. Figure 32.2.2 demonstrates this concept.

14. Refraction Refraction is the bending of light that is caused by a change in speed when the light wave goes from one medium into another. That is why things appear to be somewhere they are not underwater.

16. The Angle of Incidence is equal to the angle of reflection.

19. All objects produce electro-magnetic waves.

21. For example, as light hits your shirt the color your eye detects is the color of light that has been reflected or re-emitted by your shirt.

23. Glowing Objects Incandescent light is light that is produced as a result of a glowing hot object. Light bulbs that have filaments in them have an electric current pass through them. As a result of this electric current, the filament heats up and begins to glow, giving off light.

25. The electric current comes in at one electrode and transmit the electrons into the gases.

27. Electromagnetic Waves Characteristics of Electromagnetic Waves Transverse Waves Alternating electric and magnetic fields Characteristics of waves and particles All travel at 3.0 x 108 m/s (Speed of Light) It takes 8 minutes for light to get from the Sun to Earth It takes 3 seconds for radio signals to get from Earth to the Moon

28. Electromagnetic Spectrum Includes the following types of waves Radio Microwaves Radar Infrared Visible Light Ultraviolet X-Rays Gamma Rays

29. Radio and Microwaves Radio waves are used for radio, cell phones, remote controlled devices, GPS/satellite communications, and television. Microwaves are the shortest wavelength radio waves and are used in many communication functions. Radar is used to determine how fast an object travels. It incorporates the use of radio signals, receivers, and the Doppler effect in order to determine the speed of an object.

30. Infrared Waves Infrared waves are heat waves. All objects emit infrared waves because all objects possess heat. Night vision goggles detect infrared waves and allow the user to see the movement of objects in the dark. Many TV remotes use infrared.

31. Infrared image of a human body. Red is hot, blue is cool.

32. Visible Light Our eyes detect electromagnetic energy in a small portion of the electromagnetic spectrum called the visible light region. The visible light region corresponds the wavelengths and frequencies of red, orange, yellow, green, blue, indigo, and violet light.

33. Ultraviolet Waves UV Light that is at a higher frequency and energy than violet light. UV light can kill micro-organisms. Too much exposure can cause: Sunburn, Wrinkles, and skin cancer As it damages cell DNA

34. X-Rays X-Rays have high energy and can penetrate some material. Used in: Medicine Industry Transportation Too much exposure can damage living tissue or even cause cancer.

35. Gamma Rays Gamma rays are the highest energy electromagnetic wave. They usually come from radioactive elements or stars Uses include: Killing cancer cells Making pictures of the brain Inspection tools in industry

36. Speed of Electromagnetic Waves All electromagnetic waves travel at 3.0 x 108 m/s in a vacuum. Speed of a wave formula: Speed = Frequency x Wavelength As the frequency increases, the wavelength decreases. See the next slide for a diagram of this relationship.

37. Electromagnetic Spectrum Diagram Diagram of Electromagnetic Spectrum (including the relationship between frequency and wavelength).