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Electromagnetic Waves

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Presentation on theme: "Electromagnetic Waves"— Presentation transcript:

1 Electromagnetic Waves
Chapter 11

2 Section 1 What are Electromagnetic Waves?
Vocabulary: electromagnetic wave; photon How does a vibrating electric charge produce an electromagnetic wave? What properties describe electromagnetic waves? How do electromagnetic waves transfer energy?

3 What are Electromagnetic Waves?
Waves are produced by something that vibrates and carry energy from one place to another We learned that waves such as sound cannot move unless they have matter (or a medium) to transfer the energy through BUT there is one type of energy that does not require matter The electromagnetic wave is made by vibrating electric charges. They are composed of changing electric fields and magnetic fields

4 Properties The vibrating electric and magnetic fields of an electromagnetic wave are perpendicular to each other (pg340). This is also a transverse wave. In a vacuum, all electromagnetic waves travel at 300,000 km/s. Light is a type of electromagnetic wave which is why its called the “speed of light”. Nothing travels faster than the speed of light. Wavelength is the distance from crest to crest and frequency (hertz) is the number of wavelengths that pass a point in a second. As frequency (f) increases, the wavelength (λ) becomes smaller.

5 Matter & Electromagnetic Waves
Electromagnetic waves can make objects hot such as asphalt This energy is called radiant energy Radiant energy makes fires feel warm and enables you to see

6 Waves & Particles A wave is a disturbance that carries energy; particle is a piece of matter Albert Einstein provided an explanation to Heinrich Hertz’s experiment of creating a spark by shining light on a metal. Einstein said an electromagnetic wave can behave as a particle called a photon. A photon is a massless bundle of energy that behaves like a particle. As the frequency increases, the energy of the photon increases.

7 Section 2 The Electromagnetic Spectrum
Vocabulary: radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, gamma rays What are the main divisions of the electromagnetic spectrum? What are the properties of each type of electromagnetic wave? What are some common uses of each type of electromagnetic wave?

8 A Range of Frequencies Wide range from vibrating once each second or trillions of times each second The entire range of frequencies is called the electromagnetic spectrum Each section has a specific name (pg 345) Each region interacts with matter differently and the human eye only detects a small portion called visible light.

9 Radio Waves Longer than 10 cm Long wavelengths and low frequencies
You hear sound when your radio changes the radio wave into a sound wave Radar: Radio Detecting And Ranging; used for tracking MRI create a map of different tissues to provide an inside picture of the patient’s body which is produced painlessly

10 Microwaves Wavelengths between 0.1 mm and 30cm but 1cm to 20 cm are used in communication such as cell phones and satellites. Most familiar with microwave ovens. Microwave ovens interact with water, which is why you have a defrost setting on the microwave because the water molecules in crystallize form cannot rotate.

11 Infrared Rays You feel warmth from these wavelengths that range from about a thousandth of a meter to a about 700- billionths of a meter Hotter objects emit more infrared waves than cooler objects Used by firefighters, energy-efficiency of a structure, CD-ROM drives, TV remote controls

12 Visible Light Range you can detect with your eyes with wavelengths around 700-billionths to 400-billionths of a meter Visible light only differs from radio waves, microwaves, and infrared waves by its frequency and wavelength Color is the brains interpretation of the light absorbed by substances in the eye Short wavelengths are violet to long such as red If all colors are present in the same place, you see white

13 Ultraviolet Waves UV waves can enter cells making them both harmful and useful Can cause sunburn (UVA & UVB) but some exposure is healthy because it creates vitamin D. It can disinfect food, water, medical supplies Fluoresce power to reveal fingerprints Ozone layer

14 X-Rays Penetrate skin and soft tissues but not denser material such as teeth and bones (Low doses) Used in airport screening Can be harmful and both helpful to humans

15 Gamma Rays High frequencies and highest-energy photons
Can penetrate several centimeters of lead Produced by processes that occur in the nuclei of atoms Can be focused to an area and cause cancer cells to die which unfortunately also kills healthy cells in the process

16 Section 3 Radio Comunication
Vocabulary: carrier wave, modulation, analog signal, digital signal, transceiver, Global Positioning System (GPS) How are carrier waves modulated to transmit information? What is the difference between amplitude modulation and frequency modulation? What technologies use radio waves and microwaves for communication?

17 Radio Transmissions Each radio, cell and television station uses an assigned frequency so stations don’t interfere with each other (pg 352)- AM, FM, etc. Specific frequency to which a station is assigned is called the carrier wave Know the difference between FM and AM radios Closer to the tower the stronger the signal; bad weather, surrounding mountains and artificial structures can interfere with radio transmissions

18 The Digital Revolution
Analog signals are electric signals whose values change smoothly over time Digital signals, started in 2009, is an electrical signal where there are only two possible values, on and off. Converter boxes

19 Telephones Used to be connected with wires
Cell phones are transceivers which transmits one radio signal and receives another radio signal Pagers work in a similar fashion

20 Communications Satellites
Microwave signal is sent to the satellites and as a transceiver it sends pack to a particular region on Earth Satellite cell phones such as when crossing the ocean there are no towers to switch between; delay in two- way communications Dishes uses microwaves rather than radio waves

21 GPS System of satellites, ground monitoring stations and receivers that determine your exact location at or above Earth’s surface Need four satellites to determine the location of an object using a GPS receiver Owned and operated by USDoD but the signals sent out can be used by anyone. Pet collars, airplanes, ships, cars, etc.

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