2 1 Waves and the Electromagnetic Spectrum 7

2. 1 Waves and the Electromagnetic Spectrum 7. 6. a Students know visible light is a small band within a very broad electromagnetic spectrum.

Waves and Energy � Wave- a disturbance that transfers energy from place to place � Energy- the ability to do work � Disturbance is temporary- after wave is gone medium is calm again � Most waves require a medium to travel through � Medium- material a wave travels through � Examples of mediums: gases, liquids, solids � Waves that require a medium are mechanical waves

Waves and Energy �A wave that doesn’t require a medium is an electromagnetic wave (example: light) � Key concept: Mechanical waves are produced when a source of energy causes a medium to vibrate � Vibration- repeated back-and-forth and up-anddown motion � When a vibration goes through a medium a wave results � Energy is needed to make a wave � When waves travel though a medium the medium does NOT travel with the waves

Properties of Waves Key concept: The basic properties of all waves are amplitude, wavelength, frequency, and speed.

Properties of Waves � Amplitude- maximum distance that the particles of the medium moves away from the rest position � Crest- high point of the wave � Trough- low point of the wave

Properties of Waves Wavelength- the distance between two corresponding parts of the wave (example: from crest to crest)

Properties of Waves � Frequency- number of complete waves in a certain amount of time � Hertz-units we use when measuring frequency � Waves travel at different speeds � Speed- far the wave travels in a given amount of time � If the medium doesn’t change the speed doesn’t change

Properties of Waves

What Is an Electromagnetic Wave? Key concept: An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.

What is an Electromagnetic Wave? � They transfer energy without a medium � Electromagnetic waves- transfers electrical and magnetic energy � They are produced by charged particles � Every charged particle has an electric field surrounding it

What is an Electromagnetic Wave? � Electromagnetic radiation- energy that is transferred through space by electromagnetic waves � Electromagnetic waves travel at the speed of light (about 300, 000 kilometers per second) � They transfer energy through a vacuum or empty space � When light travels through a medium it travels slower

What Is the Electromagnetic Spectrum? The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.

Videos: • Exploring Light and Color: The Electromagnetic Spectrum • Light: The Electromagnetic Spectrum

What Is the Electromagnetic Spectrum? �More frequency means more energy � Radio waves- electromagnetic waves with the longest wavelengths and lowest frequencies (radio and TV) � Microwaves- electromagnetic waves with the shortest wavelengths and highest frequencies (microwaves and cell phones) � Infrared Rays- invisible heat (heat lamps)

What Is the Electromagnetic Spectrum? electromagnetic waves travel at the same speed in a vacuum but at different wavelengths and different frequencies � As wavelength decreases frequencies increases � Waves with the longest wavelengths have the lowest frequencies � Waves with the shortest wavelengths have the highest frequencies � All

What Is the Electromagnetic Spectrum? � Key concept: The electromagnetic spectrum is made up of radio waves, infrared rays, visible light, ultraviolet rays, X -rays, and gamma rays.

What Is the Electromagnetic Spectrum? � Visible light- small band in the broad electromagnetic wave that you can see � Main colors of visible light- red, orange, yellow, green, blue, indigo, violet

What Is the Electromagnetic Spectrum? Ultraviolet rays- wavelengths just shorter than visible light Ultraviolet rays carry more energy than visible light Exposure to small amounts of ultraviolet rays can be healthy but too much can cause skin cancer

What Is the Electromagnetic Spectrum? � X-rays- wavelengths just shorter than visible light � Has more energy than ultraviolet rays so x-rays can penetrate most things � Dense matter (like bone or teeth) absorbs x-rays and doesn't let them pass through � Gamma rays- shortest waves, most frequency, and most penetrating � Gamma rays are used to kill cancer inside the body