7.6.a Students know visible light is a small band within a very broad electromagnetic spectrum

7.6.a Students know visible light is a small band within a very broad electromagnetic spectrum.

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

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-and-down 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

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

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)

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

What Is an Electromagnetic What Is an Electromagnetic Wave?Wave? Key concept: An electromagnetic wave

consists of vibrating electric and magnetic fields that move through space at the speed of light.

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

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 What Is the Electromagnetic Spectrum?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

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)

All 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

Key concept: The electromagnetic spectrum is made up of radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.

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

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

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