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Name _________________________________________________ Period ______ Date __________________ The Electromagnetic Spectrum What is an electromagnetic wave? Light is an electromagnetic wave. Light is a wave, like sound and the ripples on a pond. What is oscillating in a light wave? Imagine you have two magnets. One hangs from a string and the other is in your hand. If you wave the magnet in your hand back and forth, you can make the magnet on the string sway back and forth. How does the oscillation of one magnet get to the other one? Magnets create an invisible magnetic field around them. When you move a magnet up and down, you make a wave in the magnetic field. The wave in the magnetic field makes the other magnet move. Oscillations of electricity or magnetism create electromagnetic waves Anything that creates an oscillation of electricity or magnetism also creates CHAPTERelectromagnetic 24: THE PHYSICAL NATURE OF LI waves. If you switch electricity on and off repeatedly in a wire, the oscillating electricity makes an electromagnetic wave. This is exactly how radio towers make radio waves. Electric The electromagnetic spectrum currents oscillate up and down the metal towers and create electromagnetic waves of theHow right does an frequency to carry radio signals. Tapping a stick up and down in a puddle makes ripples that electromagnetic wa Properties of Like all waves, electromagnetic waves (like light) have frequency, spread out wavelength, from where amplitude, you tap. Oscillating electric current in a radio tower makes ripples of electromagnetic and speed. Also like other waves, electromagnetic Electromagnetic wave electricity spread out fromfrequency. the tower at the speedoneof light as waves and wavesmagnetism carry energythat in proportion to their Shaking a magnet magnetic and electrica electromagnetic waves. million times per second (1 MHz) takes more energy than shaking it once per The two qualities exch back and forth like a p second (1 Hz). That is why a 1 MHz electromagnetic wave has a million times Properties of electromagnetic waves exchanges potential a more energy than a 1 Hz electromagnetic wave of the same amplitude. Like all waves, electromagnetic waves (like light) have frequency, wavelength, amplitude, and energy back and forth Why visible light all electromagnetic waves are invisible for carry the same reasoninyou cannot speed. AlsoAlmost like other waves, electromagnetic waves energy proportion to their chapter 17 you learne isfrequency. different Shaking see the magnetic field between magnets. The exception visible light.energy than a magnet one milliontwo times per second (1 MHz)istakes more induction; a changing Visible includes only the electromagnetic waves with the range of energy shaking it once perlight second (1 Hz). That is why a 1 MHz electromagnetic wave has a million field induces an electr can be detected the human eye. wave of the same amplitude. times more that energy than a 1 Hzbyelectromagnetic vice versa. Induction i . The The entire range of electromagnetic waves, including all possible frequencies, electromagnetic wave Why visibleislight is the different electromagnetic called electromagnetic spectrum. The electromagnetic spectrum and spread. Each cyc Almost all electromagnetic waves are invisible for the same reason you cannot see the spectrum includes radio waves, microwaves, infrared light, ultraviolet light, X rays, and electric part of the wa magnetic field between two magnets. The exception is visible light. Visible light includes only magnetic wave as it c gamma rays. Visible light is a small part of the spectrum in between infrared the electromagnetic waves with the range of energy that can be detected by the human eye. Each cycle of the mag and ultraviolet light. in turn creates a new electric wave. The ele magnetic parts of the regenerating each oth wave propagates. UNIT 8 LIGHT AND OPTICS Name _________________________________________________ Period ______ Date __________________ The electromagnetic spectrum The entire range of electromagnetic waves, including all possible frequencies, is called the electromagnetic spectrum. The electromagnetic spectrum includes radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays. Visible light is a small part of the spectrum in between infrared and ultraviolet light. Like other forms of high-energy electromagnetic waves, ultraviolet light has enough energy to remove electrons and break chemical bonds. Sunlight contains ultraviolet waves. A small amount of ultraviolet radiation is beneficial to humans, but larger amounts cause sunburn, skin cancer, and cataracts. Most ultraviolet light is blocked by ozone in Earth’s upper atmosphere. Radio waves are the lowest-frequency waves. They have wavelengths that range from kilometers down to tens of centimeters (Figure 24.4). Radio broadcast towers are tall because they need to be one-quarter of a wavelength high to efficiently create the large wavelengths of radio waves. The speed of light All electromagnetic waves travel at the same speed in a vacuum, the speed of light — 3 × 108 m/sec. As with other waves, the speed of light is the frequency multiplied by the wavelength. Questions 1. Describe an electromagnetic wave. How is one made? 2. What is the relationship between the frequency of light and its wavelength? 3. What is the speed of light? ________________. 4. Compare and contrast a radio wave and ultraviolet light. 5. Radio waves, X rays, gamma rays, and visible light are all part of the ________________. 6. ________________ is the type of electromagnetic wave that can cause sunburn. 7. ________________ are produced by oscillations of electricity or magnetism. 8. ________________ is the type of electromagnetic wave we feel as heat. 9. The part of the electromagnetic spectrum we can see with our eyes is called ________________. 10. ________________ are the highest frequency waves in the electromagnetic spectrum and are generated in nuclear reactions.