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# Light waves

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### Light waves

1. 1. LIGHT WAVES Like sound waves and waves in water, light waves can travel through matter. Light waves can travel through space that contains almost no matter.
2. 2. Electromagnetic Waves • Electromagnetic waves are waves that can travel through matter and through empty space. Light travels fastest through empty space and slowest through solids.
3. 3. Wavelength of light • Wavelength of light are usually measured in a unit called the nanometer (nm). • 1 m= 1,000,000,000 nm
4. 4. Properties of Light Waves • Light waves and all electromagnetic waves are transverse waves. • An electromagnetic wave has an electric part and a magnetic part. Both are called fields.
5. 5. • The frequency of an electromagnetic wave is the number of times the electric and magnetic fields vibrate in one second.
6. 6. • The wavelength of an electromagnetic wave is the distance between the crests or troughs of the vibrating electric or magnetic parts.
7. 7. Intensity of Light • The intensity of wave is a measure the amount of energy that the waves carry. The intensity of light waves tell how bright a light is. A dim light has lower intensity. Its waves carry less energy. A bright light has higher intensity. Its waves carry more energy.
8. 8. Electromagnetic Spectrum • There are many kinds of electromagnetic waves. • The electromagnetic spectrum is made of all the frequencies and wavelengths of electromagnetic waves.
9. 9. • At one end of the spectrum are the waves that have the lowest frequency. They also have the lowest energy and the longest wavelength. At the other end of the spectrum are waves that have the highest frequency. They also have the highest energy and the shortest wavelength.
10. 10. Radio Waves • Radio waves have the lowest frequency on the electromagnetic spectrum. They are on the left side of the electromagnetic spectrum. They carry television and radio signals into your home. These waves have the longest wavelength.
11. 11. • The shortest radio waves are called microwaves. Microwaves are used to cook food in microwave ovens. They also carry information to and from cell pones.
12. 12. Infrared Waves • You use infrared waves when you use a remote control to change the channel on your television. Infrared waves carry information from the remote control to the television.
13. 13. • There are special night goggles that pick up infrared waves. They can be used to see people in the dark.
14. 14. Visible Waves • There is part of the electromagnetic spectrum that people can see called visible light.
15. 15. • The color of the light you see depends on the wavelength of the light waves. Violet light has the shortest wavelength. Red light has the longest wavelength.
16. 16. • The light from the Sun or from a flashlight is white light. White light is a combination of different colors. You see this as a rainbow of colors coming out of the prism.
17. 17. Ultraviolet Waves • Ultraviolet waves are shorter and carry more energy than visible light waves. • There are ultraviolet waves in sunlight. Some exposure to ultraviolet waves is good for you. • Ultraviolet waves help your body make vitamin D. You need vitamin D to keep your teeth and bones healthy.
18. 18. • But, ultraviolet waves can give you a sunburn if you stay out in the sunlight too long. Too much sunlight can damage our skin and even cause skin cancer.
19. 19. X Rays and Gamma Rays • X rays and gamma rays have the highest energy, highest frequency, and shortest wavelengths of all the waves in the electromagnetic spectrum.
20. 20. • Doctors use X rays to see broken bones. X rays have enough energy to go right your skin. But, they cannot pass through dense objects, such as bones. This allows X rays to produce an image of the inside of your body.
21. 21. • Gamma rays have even more energy than X rays. Gamma rays are used on some foods to kill bacteria that make food spoil quickly.