The Electromagnetic Spectrum

Chapter 24, Section 1

What is the electromagnetic spectrum?

The spectrum arrangement of electromagnetic radiation ... according to their wavelengths and frequencies.

Why is understanding light important to astronomers?Most of what we know about the universe is the result of studying distant light sources.

The arrangement of electromagnetic waves according to wavelengths and frequencies is called ...the electromagnetic spectrum.

List the types of energies ...

FALSE

Different magnetic waves all travel the same speed through a vacuum.C = the speed of light3.00 x 108  m/s2

Light ...

Sometimes behaves like waves.Sometimes behaves like particles.Called photons when it behaves like particles.Either/or. Never acts like both, at the same time.

Getting wavelengths from light.

Light is made up of different wavelengths.To separate, you will need a diffraction surface.Ex: Prism

Getting wavelengths from light.

Light is made up of different wavelengths.To separate, you will need a diffraction surface.Ex: Diffraction Grating (aka Rainbow Glasses)

Light as Particles

Called PHOTONSIndicated with a squiggly line

Wavelength

The distance from one wave crest (top of the wave) to anotherMeasured in nanometers (nm)1 nm = 10-9 m

Frequency

Frequency = how many wave crests (top of the wave) will pass through a point in space in one second (Hz)The shorter the distance between crests, the more that can pass through

How are Frequency and Wavelength Related?The shorter the ________, the higher the ____________.

How are Frequency and Wavelength Related?The shorter the ________, the higher the ____________.

X-rays and Gamma Rays

Are ultra-high-frequency electromagnetic waves that can travel through matter, break molecular bonds, and damage cells.X-Rays are used to provide images of bones and to examine suitcases at airports without opening them.Radiation therapy is used to kill diseased cells.

Spectroscopy

Each light spectrum is unique to the material producing it.Can use spectrum as a “fingerprint” to figure out what material it is.Three types of spectra.

Continuous Spectrum

A solid object, when heated up, will produce a continuous spectrum with all wavelengths.Example: light bulb (the wire is a solid object)

Continuous Spectrum

A solid object, when heated up, will produce a continuous spectrum.Example: metal

Continuous Spectrum

A solid object, when heated up, will produce a continuous spectrum.Example: rock (lava)

Blackbody Radiation

Every thing emits light all the time.Normally, you don't notice because at comfortable temperatures, most of the light is infrared (invisible to the human eye).At higher temperatures, objects start emitting more visible light.The higher the temperature, the more high frequency light is emitted.

Absorption Spectrum

When a continuous spectrum passes through a gas.The gas steals (absorbs) some of the wavelengths of light.The continuous spectrum now has gaps where those wavelengths used to be.

Absorption Spectrum

Gaps tell you which gas the light went through.

Absorption & Astronomy

Emission Spectrum

When a gas is heated, it will put off only certain wavelengths of light.Stars are spheres of hot gas.

Main Sequence Emission Spectrum

Notice Anything?

What can a star's spectrum tell astronomers?Tells astronomers the chemical elements present in the star.

Doppler Effect

When the source or the “listener” is in motion it produces a distortion of wavelength called the doppler effect.

http://www.youtube.com/watch?v=-t63xYSgmKE

http://www.youtube.com/watch?v=Man9ulEYSgk&feature=related

How is the Doppler effect used in astronomy?It helps determine if something is moving toward or away from us.