Chapter 3: The Electromagnetic Spectrum Section 2: Waves of the Electromagnetic Spectrum

I. What is the Electromagnetic Spectrum. A I. What is the Electromagnetic Spectrum? A. All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies. 1. Visible light = radiation in the wavelengths you can see a. small portion of electromagnetic radiation is visible light b. Rest is invisible 2. Different wavelengths for different types of waves. 3. recall: speed = wavelength x frequency a. so, as the wavelength decreases, the frequency increases

a. Waves with the longest wavelengths have the lowest frequencies b a. Waves with the longest wavelengths have the lowest frequencies b. amount of energy carried by and EMW increases with frequency B. The electromagnetic spectrum- is the complete range of electromagnetic waves placed in order of increasing frequency. 1. The electromagnetic spectrum is made up of radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.

II. Radio Waves A. Radio Waves- are the electromagnetic waves with the longest wavelengths and lowest frequencies. 1. Example a. Broadcast waves: radio and television b. Microwaves 2.Broadcast waves- these are radio waves with longer wavelengths. a. Radio or TV antenna picks up these waves at certain frequencies b. Then converted to an electrical signal which is converted to sound (radio) sound and picture (TV)

B. Microwaves – radio waves with the shortest wavelengths and the highest frequencies 1. used in cooking, radar, and cellular phone communication a. Radar = radio detection and ranging b. Radar – is a system that uses reflected radio waves to detect objects and measure their distance and speed. 1. distance determined by how long it takes the reflected waves to return to the device 2. Speed determined by the doppler effect a. Frequency of reflected waves off of car is different from the original waves b. Difference in frequency is the speed

III. Infrared Rays A. Infrared rays- are electromagnetic waves with wavelengths shorter than those of radio waves. 1. have more energy than radio waves bc they have a higher frequency Ex: the invisible heat (infrared radiation) you feel as burner warms up before you see the glow B. Heat lamps: 1. bulbs give off infrared rays (often called heat rays) and very little visible light.

B. Infrared Cameras- 1. take pictures using infrared rays instead of light a. Most objects give off some infrared rays. 2. thermogram- an image that shows regions of different temperatures in different colors 3. used to see objects in the dark 4. firefighters use infrared cameras to locate fire victims inside a dark or smoky building.

Visible Light A. Visible light – electromagnetic waves you can see 1. shorter wavelengths and higher frequencies than infrared rays a. Red light = longest wavelengths b. All other colors appear as the wavelengths decrease c. Violet light = shortest wavelength d. White light = mixture of many colors 2. use a prism to separate out white light from the sun a. Waves bend as they enter a new medium b. Therefore, the prism refracts different wavelengths by different amounts and separates them into different colors. 1. red light waves refract the least 2. violet light waves refract the most

V. Ultraviolet Rays A. Ultraviolet rays – electromagnetic waves with wavelengths just shorter than those of visible light. 1. have higher frequencies than visible light = more energy 2. energy is great enough to damage or kill living cells. Ex: UV lamps used to kill bacteria on hospitals equipment 3. small doses of UV is beneficial to health: produces vitamin D (needed for teeth and bones) 4. large doses is dangerous = burn skin, cause skin cancer, damage eyes

VI. X-Rays- A. X-Rays- are electromagnetic waves with wavelengths just shorter than those of ultraviolet rays. 1. have higher frequencies and carry more energy than UV rays 2. can penetrate most matter a. Except bone or dense matter = absorbs the x-rays = does not pass through 3. too much exposure to x-rays can cause cancer 4. lead apron absorbs x-rays preventing them from reaching your body

VII. Gamma Rays A. Gamma rays- are the electromagnetic waves with the shortest wavelengths and highest frequencies 1. most penetrating of all electromagnetic waves 2. can be produced from some radioactive substances and nuclear reactions 3. used in medicine: kill cancer cells a. Patient injected with a fluid that emits gamma rays = forming an image inside the body 4. Explosions of starts are thought to produce gamma rays in the space

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