Unit 6 Electromagnetic Radiation:
Electromagnetic Radiation is a wave. Electromagnetic Radiation is not a mechanical wave. Does not need a medium. Can travel through empty space
Examples of Electromagnetic Radiation X-rays, Visible light, microwaves, radio waves, Ultra violet, gamma rays and infrared. They are all types of electromagnetic radiation.
Electromagnetic Radiation We are constantly bombarded by electromagnetic radiation, most of which we cannot see. Note http://www.epa.gov/radtown/enter-radto
Electromagnetic Radiation Radiation can be described as the movement of energy through space. There are many different sources of radiation that vary by intensity. The Sun, light bulbs, nuclear reactions, and radon gas, are all sources that produce electromagnetic radiation. We are constantly bombarded by electromagnetic radiation, most of which we cannot see.
Electromagnetic Radiation Not all electromagnetic radiation we interact with is bad. When you cook food in a microwave, listen to music, see colors, or feel heat, you are experiencing electromagnetic radiation. How do you think electromagnetic radiation travels through space?
Electromagnetic Radiation Electromagnetic radiation travels through space as a wave. Electromagnetic waves are different from mechanical waves because they don't need a medium to travel through. What's "waving" in an electromagnetic wave?
Electromagnetic Waves Electromagnetic waves are produced by vibrating electric charges. When an electric charge vibrates, its electric field changes, producing a changing magnetic field. The electric and magnetic field are perpendicular to each other. The changing magnetic field produces a changing electric field. The changing electric field produces a changing magnetic field. And so on and so on and so on...creating a transverse electromagnetic wave.
How Electromagnetic Waves Travel This means electromagnetic waves can travel through empty space as well as through mediums like air or water! Electromagnetic waves also do not lose energy as they travel. This is unlike mechanical transverse waves which lose some of their energy to their medium. An electromagnetic wave continues to go straight and spread out until it collides with some form of matter, at which point the direction of travel will change.
Electromagnetic Wave Characteristics Electromagnetic waves have the same wave characteristics we studied last unit: wavelength (λ) measured in meters frequency (f) measured in Hz speed (c) 300,000,000 meters/second Wavelength and frequency vary based on the type of electromagnetic wave, but all electromagnetic waves travel at the same speed in a vacuum. What is a vacuum? Hint: Not this!
The Vacuum of Empty Space A vacuum is a space that is completely empty and contains no matter.
Speed of Electromagnetic Radiation All electromagnetic radiation travels at 300,000,000 meters per second in a vacuum. This is also know as the speed of light. abbreviated (c). Nothing can travel faster than the speed of light. electromagnetic waves slow down when encountering any matter. If you could travel at the speed of light, you could go around Earth's equator 7.5 times in one second.
Wavelength of Electromagnetic Radiation Different types of electromagnetic radiation have different wavelengths. Drag and drop the terms into the correct place on the wave. Answer wavelength crest trough
Frequency of Electromagnetic Radiation Different forms of electromagnetic radiation have different wavelengths, and different frequencies. Radio waves have large wavelength and low frequency Xrays = small wavelength and high frequency Notice there is an inverse relationship between wavelength and frequency. As one value goes up, the other goes down. For example, the longer the wavelength, the lower the frequency.
Speed, Wavelength and Frequency A wave's frequency or wavelength can be solved for using the wave equation from last unit: Since all electromagnetic radiation travels at the speed of light, v can be replaced with this value every time, represented by the letter c, which equals 300,000,000 m/s.
Speed, Wavelength and Frequency We use the new wave equation to solve for the frequency or wavelength of electromagnetic waves based on the equations below: or Click here to watch a video that proves the speed of light by using chocolate and a microwave!
1 If you could travel at the speed of electromagnetic waves in a vacuum, how long would it take you to travel from the surface of Earth to the Moon? speed = c = 300,000,000 m/s distance between Earth and Moon = 356,400 km or 356,400,000 m t = d/s Answer
2 The Sun is 149,600,000 km away from Earth. How many minutes ago did the radiation that is hitting you right now leave the Sun? Students type their answers here c = 300,000,000 m/s Answer
3 Radio waves are electromagnetic waves with long wavelengths. If an AM radio wave's frequency is 540,000 Hz, what is its wavelength? Is it long enough to bounce over the Empire State Building (381 m)? c = 300,000,000 m/s Answer
4 What is the frequency of a radio wave that has a wavelength of 1 cm (0.01 m)? Answer
5 An electromagnetic wave has a frequency of 1.5 GHz (1,500,000,000 Hz). What is the wavelength of the wave? (1 GHz = 1,000,000,000 Hz) Answer
6 Red light has a frequency of 4.6 x 10 14 Hz (460,000,000,000,000 Hz). What is the wavelength of red light? Answer
7 Which of the following electromagnetic wavelengths would have the highest frequency? A 100 m B 10 m C 1 m D 0.1 m Answer
8 Which of the following frequencies would have the shortest wavelength? A 1000 Hz B 100 Hz C 10 Hz Answer D 1 Hz