Electromagnetic Waves An Electromagnetic wave is a wave that consists of vibrating electric and magnetic fields. They are considered to be transverse waves

Electromagnetic Waves Transverse waves without a medium! (They can travel through empty space)

They travel as vibrations in electrical and magnetic fields. Have some magnetic and some electrical properties to them.

When an electric field changes, so does the magnetic field When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other. RESULT-An electromagnetic wave.

The Electromagnetic Spectrum Presentation for lesson 4: Exploring the Electromagnetic Spectrum, in the Waves: The Three Color Mystery unit The slides are animated so you can click (space bar, mouse, etc.) to show the next item when the class is ready. The Electromagnetic Spectrum

WHAT IS WAVELENGTH THE DISTANCE BETWEEN THE CREST OF THE WAVES IS CALLED THE WAVELENGTH. THE FARTHER THE DISTANCE, THE SLOWER THE WAVE MOVES. SLOWER WAVES ARE LESS DAMAGING TO HUMANS

WHAT IS AMPLITUDE? WHAT IS FREQUENCY? AMPLITUDE IS THE HEIGHT OF THE WAVE: THAT IS FROM THE CREST TO THE TROUGH (THE BOTTOM OF THE WAVE FREQUENCY IS THE NUMBER OF WAVES THAT CROSS A GIVEN POINT IN A GIVEN TIME. For example: fewer radio waves will pass a given point than gamma rays: The higher the frequency, the more harmful the type of electromagnetic wave.

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency GAMMA RAYS ULTRAVIOLET RAYS RADIO WAVES INFRARED RAYS X-RAYS MICROWAVES VISIBLE LIGHT

Do you remember frequency and wavelength?

The Electromagnetic Spectrum longest wavelength shortest wavelength The Electromagnetic Spectrum The waves with the LONGEST wavelength (radio waves) are on the LEFT. The waves with the SHORTEST wavelength (gamma waves) are on the RIGHT.

Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

Characteristics of Radio waves: longest wavelength shortest wavelength Characteristics of Radio waves: *Longest wavelength & Lowest Frequencies *Two Types: 1. Broadcast Waves – radio & TV 2. Microwaves

Characteristics of Microwaves: longest wavelength shortest wavelength Characteristics of Microwaves: *RADIO waves with the Shortest Wavelength & highest frequency *Uses: -Microwave Oven -Cell Phone -Radar – system that uses reflected radio waves to detect objects and measures their distance and speed

A radio picks up radio waves through an antenna and converts it to sound waves. Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.

Global Positioning Systems (GPS) Magnetic Resonance Imaging (MRI) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite. Magnetic Resonance Imaging (MRI) -Uses Short wave radio waves with a magnet to create an image.

Characteristics of Infrared waves: longest wavelength shortest wavelength Characteristics of Infrared waves: -shorter wavelength than microwaves. -felt as heat (stoves) -Two Types- 1. Heat Lamps – food, warm bathrooms 2. Infrared Cameras – takes pics of infrared rays not light Infrared waves (heat): Have a shorter wavelength, from .001 m to 700 nm, and therefore, a higher frequency. Used for finding people in the dark and in TV remote control devices

Heat lamps give off infrared waves. Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Heat lamps give off infrared waves. Therefore people give off infrared rays.

Characteristics of Visible light: longest wavelength shortest wavelength Characteristics of Visible light: -Electromagnetic waves that you can see -shorter wavelengths and higher frequencies than infrared rays -Seen as colors. *red – longest wavelength; violet – shortest wavelength

Visible Light: Remembering the Order ROY G. BV red orange yellow green blue violet White light from the sun is separated by a prism into colors of the visible spectrum. Prism refracts light based on wavelengths Red refracts the least. Violet refracts the most.

Characteristics of Ultraviolet light: longest wavelength shortest wavelength Characteristics of Ultraviolet light: -shorter wavelength & higher frequencies than visible light -Carries A Lot of Energy  can damage or kill living cells *kills bacteria on hospital equipment *small amounts can be good  cause skin cells to produce Vit D *Too much can be bad  burns skin, causes cancer, damages eyes

Characteristics of X-ray radiation: longest wavelength shortest wavelength Characteristics of X-ray radiation: -shorter wavelength than ultraviolet. -pass through skin, not bone or lead. -Too much exposure can be harmful to humans (cancer) -Sometimes used in industry & engineering

Used by engineers to check for tiny cracks in structures. Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed) Used by engineers to check for tiny cracks in structures. The rays pass through the cracks and the cracks appear dark on film.

Characteristics of Gamma radiation: longest wavelength shortest wavelength Characteristics of Gamma radiation: -shortest wavelength/highest frequency (highest energy) -from radioactive substances or nuclear reactions. -Greatest amount of Energy  most penetrating -used to kill cancer cells in the human body -can be harmful to humans. -some objects in space emit bursts of gamma rays -blocked by Earth’s atmosphere  seen by telescopes

Gamma Rays This picture is a “scintigram”  It shows an asthmatic person’s lungs. The patient was given a slightly radioactive gas to breath, and the picture was taken using a gamma camera to detect the radiation. The colors show the air flow in the lungs.

GAMMA RAYS Exploding nuclear weapons emit gamma rays. Carry the greatest amount of energy and penetrate the most. Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly Exploding nuclear weapons emit gamma rays.

Brief SUMMARY A. All electromagnetic waves travel at the same speed. (300,000,000 meters/second) in a vacuum. B. They all have different wavelengths and different frequencies. Long wavelength-lowest frequency Short wavelength highest frequency The higher the frequency the higher the energy.