Section Electromagnetic Waves and the Electromagnetic Spectrum

Transcription

1 Section 18.6 Electromagnetic Waves and the Electromagnetic Spectrum

2 Electromagnetic Waves Electromagnetic Waves Electromagnetic waves are transverse waves produced by the motion of electrically charged particles called photons. Electromagnetic waves do not require a medium and are therefore able to travel at the speed of light. The speed of light = 3 x 10 8 m/s (300,000,000 m/s)

3 Electromagnetic Waves At this speed it can go around the world 8 times in one second.

4 Electromagnetic Waves Intensity The intensity of light decreases as energy travel farther from the source The Waves of the Spectrum The different electromagnetic waves are arranged in the electromagnetic spectrum. The electromagnetic spectrum is arranged in order of increasing frequency and decreasing wavelength. The higher the frequency, the more energy per wave, and the more potentially harmful the wave is.

5 Electromagnetic Spectrum Low Energy High Energy

6 Electromagnetic Spectrum Each kind of wave is characterized by a range of increasing frequency from left to right. Radio Waves (Low Energy) Microwaves Infrared Rays Visible Light Ultraviolent rays X-Rays Gamma Rays (High Energy)

7 Radio Waves Radio waves are the lowest frequency and longest wavelength in the spectrum. They are used primarily for communications, such as cell phones, T.V. and radio transmissions, and cordless devices such as phones, speakers, etc.

8 Radio Waves Include AM and FM radio stations AM: Amplitude Modulation The frequency waves stay the same and the amplitude of the wave is varied

9 Radio Waves Include AM and FM radio stations FM: Frequency Modulation The amplitude waves stay the same and the frequency of the wave is varied.

10 Microwaves Microwaves are a type of radio wave. They are used in cell phones and microwave ovens. At normal levels, microwaves are harmless.

11 Infrared Infrared radiation transfers energy in the form of heat. Examples include heat lamps and the warmth from the sun. Special types of film and cameras can show infrared radiation.

12 Visible Light Visible light can be separated into 7 different colors From lowest frequency to highest, they follow the acronym: ROY G. BIV When all 7 colors are combined together they produce white light. When all 7 colors of the spectrum are absent, then the color black is produced.

13 Ultraviolent (U.V.) Rays Ultraviolent (U.V.) rays have applications in health and medicine, and in agriculture. U.V. rays are potentially dangerous at high levels or with prolonged exposure. U.V. rays can cause sunburns and skin cancer, and kill bacteria and healthy cells.

14 X-Rays X-Rays are used in medicine, industry, and transportation to make pictures of the inside of solid objects. X-rays are potentially dangerous at moderate levels. X-rays can penetrate many materials such as skin, muscle, and many fabrics

15 Gamma Rays Gamma radiation is high frequency waves which can be extremely dangerous. Gamma rays are used in the medical field to kill cancer cells and make pictures of the brain and in industrial situations as an inspection tool. Destructive radiation from nuclear explosions Radio waves are the highest frequency and shortest wavelength in the spectrum.

16 18.6 Assessment Question #1 How are electromagnetic waves different from mechanical waves? Electromagnetic waves do not require a medium Question #2 What is the speed of light? 3 x 10 8 m/s

17 18.6 Assessment Question #3 How do electromagnetic waves differ from one another? Each kind of wave is characterized by a range of increasing frequency Question #4 What happens to the intensity of light as energy moves away from the light source? The intensity of light decreases as energy travel father from the source

18 18.6 Assessment Question #5 List each wave in the Electromagnetic spectrum from lowest energy to highest energy. Radio Waves (Low Energy) Microwaves Infrared Rays Visible Light Ultraviolent rays X-Rays Gamma Rays (High Energy)