SPECTROSCSPECTROSCOPYOPY

Building a Simple Spectroscope

Spectroscopes are used, like prisms, to spread light out into its

component colors. By analyzing these colors, we are able to

determine the composition of everything from stars to streetlights.

Each element makes a different spectral image. Each element makes a different spectral image. This can be considered like an element’s This can be considered like an element’s fingerprint! Here’s just a few examples.fingerprint! Here’s just a few examples.For example, Iron (Fe) would look like: For example, Iron (Fe) would look like:

Carbon (C) would appear as:Carbon (C) would appear as:

Magnesium (Mg) would look like:Magnesium (Mg) would look like:

Now, let’s make our own spectroscope so that we can analyze the various light sources around us.

And remember …NEVER look directly at the sun with

your spectroscope!

Constructing a simple Constructing a simple spectroscopespectroscope

Materials needed:Materials needed: Cardboard tube (a toilet paper or paper towel roll Cardboard tube (a toilet paper or paper towel roll

will do)will do) A piece of black construction paper (or cardboard)A piece of black construction paper (or cardboard) An Exact-o Knife (or straight-edge razor blade)An Exact-o Knife (or straight-edge razor blade) Colored-pencil (white works best)Colored-pencil (white works best) ScissorsScissors Tape Tape GlueGlue Old CD, which we will use as a diffraction gratingOld CD, which we will use as a diffraction grating

From the black construction From the black construction paper, cut two squares. Each paper, cut two squares. Each should be 8cm by 8cm.should be 8cm by 8cm.

Find the center of the first Find the center of the first square by drawing an X from square by drawing an X from opposite corners. Then, draw opposite corners. Then, draw a rectangle as shown in the a rectangle as shown in the image that is no more than image that is no more than 0.2 cm wide and about 1.5 0.2 cm wide and about 1.5 cm long.cm long.

Use the exact-o knife (or Use the exact-o knife (or razor blade) to cut out the razor blade) to cut out the rectangle.rectangle.

*** Be very careful … the *** Be very careful … the blade is extremely sharp!blade is extremely sharp!

In the center of the In the center of the second square of black second square of black construction paper, cut construction paper, cut a 1 cm square hole. a 1 cm square hole.

You may find it helpful You may find it helpful to draw an X again to to draw an X again to ensure your square is ensure your square is centered.centered.

To prepare the diffraction grating you will To prepare the diffraction grating you will need a piece of CD. It can be obtained by need a piece of CD. It can be obtained by peeling off the silvery film in the upper peeling off the silvery film in the upper part of a CD. Be careful not to scratch it part of a CD. Be careful not to scratch it as it is very delicate…as it is very delicate…

Carefully cut a 2 cm by 2 cm square of diffraction Carefully cut a 2 cm by 2 cm square of diffraction grating, and tape the grating over the 1cmgrating, and tape the grating over the 1cm22 opening opening of the construction paper. of the construction paper.

Then, glue both squares to either end of the tube. It Then, glue both squares to either end of the tube. It is very important that both pieces is very important that both pieces are sealed well as not to let are sealed well as not to let light in.. light in..

Light should only be able toLight should only be able topass through the slit to the pass through the slit to the diffraction grating.diffraction grating.

Point the slit Point the slit toward a source toward a source of light, of light, with the with the diffraction diffraction grating close to grating close to your eye…your eye…

What can you What can you see?see?

If you point the spectroscope to a filament lamp…

you will see a continuum spectrum!

If you point the spectroscope to a gas lamp you will see a spectrum with lines.

Using different types of light sources, you will see different lines in the

spectrum…

And if And if you point the spectroscope to the sky…

Hands on Science Hands on Science Jan. 03, 2011Jan. 03, 2011

Sodium street lightsSodium street lights Compare daylight to a light bulb.Compare daylight to a light bulb. Different light bulbs look different (that’s why Different light bulbs look different (that’s why

energy saving bulbs light up the room in a energy saving bulbs light up the room in a different way).different way).

Neon signs.Neon signs. TV  and computer screens.TV  and computer screens. LEDs from computers or remote controls LEDs from computers or remote controls

(these give very pure spectra, often only one (these give very pure spectra, often only one color).color).

Other cool things to look at with your Spectroscope: