Electromagnetic Spectrum

Radiation – energy moving from a source as a wave

Light is a combination of electric and magnetic energy.

Light can behave as both a particle and a wave. The particle is a packet of light called a photon.

Two main properties of light:Brightness (intensity)

- amount of energy carried by light

- determined by the height (amplitude) of the wave OR- the number of photons

Color

ColorColor of light is determined by its

wavelength (λ).

Wavelength – the distancefrom crest to crest

Frequency – the number of crests passing a givenpoint in a second (measured in cycles per second OR Hertz -Hz)

Amplitude – distance from the center of the wave to the crest or trough

Velocity (speed) of a wave:

The velocity of a wave can be calculated using the formula:V= ν λWhere V = velocity ν = frequency and λ = wavelength

The speed of light is 3.0x10-8 m/s.This is actually the speed of ALL wavelengths of all of the different types of radiation- including light.Because the velocity is the same, as wavelength increases, frequency decreases.

Electromagnetic Spectrum

The electromagnetic spectrum spans longer and shorter than the visible spectrum.

Types of Radiation

Gamma Rays (γ)- High Energy radiation- The “dangerous” radiation from nuclear decay, nuclear reactors, and bombs.- Gamma radiation can be stopped by several feet of concrete, or many inches (7-8 or so), of lead.

X Rays

• X rays go through “stuff” such as skin, and clothing. Depending on the density of the “stuff” film is exposed in different amounts.

• From the following x-rays- you can see the skin ( barely) bones ( quite well) and even metal- (very clearly) as X rays do not pass easily through very dense objects- such as metal, etc.

Ultraviolet (UV) radiation

What is the most important source? The Sun

What protects the earth from UV radiation?

The ozone layerU.V. radiation is bad because it causes:

Skin cancer

Visible SpectrumRed, Orange, Yellow, Green, Blue, Indigo, VioletROYGBIV

Red – longer wave lengthBlue – shorter wavelength

White light is a mixture of all colors.

Infrared Radiation

Infra- beyondInfrared is a larger wavelength than red.We can’t perceive it, but some animals

such as snakes can. Infrared radiation I.R. is used in remote

control devices and heat lamps. This way McDonalds can cook a

hamburger 4 hours ago, and keep it hot for you!

Microwaves

Microwave radiation has been used in communication as well as …Cooking popcorn!Microwaves cause water molecules (in food) to vibrate and thus heat up.

Radar Radars send out a signal, it hits an object and reflects back to the sender.Knowing that the signal travels at the speed of light (really fast!) a computer can determine how fast an object is moving based on the time it takes for a signal to get back to the receiver.

“Stealth” planes use radar absorbing substances on their surfaces, and lots of funky angles to prevent radar signals from getting back to the receiver, thus making it hard to detect.

Television

Analog signalsUse a typical electromagnetic radiation beamed from a TV station to a tower, or a satellite, then beamed to your rabbit ears antennae.

Radio waves

Radio waves come in a large range of sizes. They can be produced by stars, galaxies,

nebulae, and black holes, therefore radio telescopes can be used to study stars and galaxies.

• Several types of radio signals• Shortwave- perhaps still used by

amateur radio operators• FM radio - Frequency Modulation• AM radio - Amplitude Modulation