SPECTROSCOPY

Prepared by:

Miss Sasha Dofflemeyer

Earth Science Bell-to-Bell Lesson

Class of Mr. Stephen Deer

Held on October 16, 2009

3rd Block

Definition

The definition of spectroscopy is the study and analysis of spectra.

The formal definition of the word spectrum means a band of

the various colors of light.

This spectrum can be visible when white light passes through a glass prism and produces a rainbow of colors:

red, orange, yellow, green, blue, and

violet.

In spectroscopy, here are a few of the definitions you must know to fully understand the subject matter.

What is light?

Light is a disturbance of electric and magnetic fields that

travels in the form of a wave. This is called a light wave.

What are the parts of this wave?

wavelength - the distance between two wave crests.

frequency - the number of times a specified periodic phenomenon occurs

within a specific interval. 1 interval

10

15

1

continuum spectrum

The science of light.

In spectroscopy, a spectroscope is used to separate the light into a series of

lines called the spectrum.

In terms of modern usage, spectroscopy is defined as the technique used to capture and analyze the light from an astronomical body.

Look through here

Marked scale to read spectra

Slit opening

Top View

Front View

SpectroscopeDiffraction grating

emissions spectrum of elements

Each element has a unique emissions spectrum. It is

emitted by hot dilute gas. The spectrum of any given element depends

on the relative intensity of electromagnetic radiation of each frequency emitted by atoms or molecules by that

element when they are excited.

absorption spectrum of elements

Each element has a unique absorption spectrum. It is an

accompaniment to the emissions spectrum. It consists of dark lines superimposed on a continuum spectrum. The spectrum is produced when a

continuum spectrum travels through cool, dilute gas.

emission spectrum of hydrogen.

emission spectrum of iron.

Astronomers use spectroscopy to classify stars.

By analyzing the spectrum of astronomical objects, Earth-bound science has been able to determine:

• the temperature and chemical makeup of the stars. • star velocities relative to our own.

• confirm that the Universe is expanding.

Temperature

Chemical Makeup

How can scientists determine a star’s chemical composition from spectroscopy?

star spectra

Did you guess Hydrogen and Magnesium?

You are correct!

λν = v

Star Velocities

Where: λ (lambda) = wavelength ν (nu) = frequency v (ve) = velocity

Expansion of the Universe

A spectrum can tell astronomers what an object is made of, how hot it is, how fast it is moving, and a host of other important attributes.

red shift -

blue shift -

An increase in the wavelength of radiation emitted by a celestial body as a consequence of the Doppler effect.

A decrease in the wavelength of radiation emitted by a celestial body as a consequence of the Doppler effect.

Expansion of the Universe

• Spectroscopy revealed the expansion of the universe.• When an object moves away from us, the lines in its spectrum get displaced toward longer wavelengths.• The amount of this so-called redshift is proportional to the object’s velocity.• Edwin Hubble first showed that the spectrum of almost every galaxy is shifted to the red.

• The farther away the galaxy, the greater the redshift.• From these observations, astronomers correctly concluded that the universe was expanding.

additional examples emission spectra of elements:

http://jersey.uoregon.edu/vlab/elements/Elements.html

Works Cited

College of William and Mary. Physics Department Physics 177 Introductory Astronomy Laboratory.

Holt, Rinehart, and Winston. Modern Earth Science. CNN. 2000: Austin

http://jersey.uoregon.edu/vlab/elements/Elements.html accessed on 10/10/2009

http://en.wikipedia.org/wiki/Atomic_emission_spectrum

http://education.yahoo.com/reference/dictionary/entry/frequency

http://amazing-space.stsci.edu/resources/explorations/light/star-light-science.html

http://www.pbs.org/wnet/hawking/strange/html/spectro.html

Questions?