A Simple Spectroscope

This activity will be useful for teachers and students alike.

If you teach science to younger students, or are in charge of physical science activities, this simple project will be a helpful hands-on teaching tool that will allow you to introduce several topics, including:

- Electromagnetic Radiation (Light)

- Diffraction

- Emission & Absorption

- Emission Spectra

Students can have a tangible example of the lesson to experiment with while you explain what they see.

Also, if you are a student looking for a simple but not too common science project, you can use this one!

The Materials you will need to build the spectroscope are:

- Cardboard Box

- Metal Tape. Also called aluminum tape, and can be bought at a home improvement store.

- Box Cutter

- Diffraction Grating. A pack of several of these diffraction grating slides are available on amazon for $13.

You will also want these few things (not in picture):

scissors, scotch tape, a ruler, and a pen/sharpie.

Now we will begin making the spectroscope.

- First, a few inches from one side of the box, draw a small, thin, vertical rectangle.

- Now, directly across from the vertical rectangle, trace the diffraction grating slide. Try to draw a smaller area inside that that is approximately the same size as the actual transparent plastic.

- Using a box cutter/razor blade/sharp knife, cut out the thin, vertical rectangle on one side, and the smaller area on the other.

- Tape the diffraction grating slide over the hole on the side that you traced it. Regular scotch tape is fine for now.

Refer to the pictures for clarity.

This step will require the metal tape (aluminum tape).

This step is important because it keeps any unwanted light from entering the spectroscope. Aluminum tape is used for the purpose because it is very reflective.

Simply put aluminum tape on the following places:

1) All the seams of the box.

2) Around the diffraction grating (but not covering it).

3) Around the thin rectangular slit (but not covering it).

4) Anywhere else you think light may enter the box.

Again, refer to the pictures for clarity.

Point the thin slit at a light source (light bulb, lamp, etc.) and look through the transparent diffraction grating. You will see light diffracted on the right and left sides. You can take pictures of what you see with a smart phone.

Observe the difference between what you see from different light sources (LED bulb vs halogen bulb vs mercury lamp, for example). The pictures above are from an LED light bulb and a halogen light bulb. Notice the fatter yellow band in the second two pictures as opposed to the first two.

I don't recommend trying this on the sun. :)

There are several types of light sources that will make interesting comparisons. Perhaps the most fun experiment that you can do with this is chemical burn tests.

Good types of chemicals for this experiment are salts. The ones in the picture came from homesciencetools.com. They are Lithium Chloride, Strontium Chloride, Calcium Chloride, and Potassium Chloride. Another one you can use is just table salt (Sodium Chloride).

A couple safety notes for the very young, inexperienced, or um... special:

-- Just because something is called a salt does not mean you can eat it.

-- Don't just use random chemicals, as you will be burning them. Just don't.

-- Be very careful with open flames.

Hopefully obvious safety advice aside, have fun burning things!

Soak a wooden burn stick in water so that it won't burn and coat it with a salt. Hold the burn stick in a fire (a gas stovetop or lighter is best) so that the salt burns. Depending on the type of salt, the flame will be a certain color. Strontium Chloride is my personal favorite -- it burns a lovely red.

Use your spectroscope and a camera or cell phone to take pictures of the diffracted emission spectrum of each burning chemical. Compare the spectra to see what colors are emitted by each chemical.

While you observe your results, take the time to learn and understand what you see. This is a good opportunity to introduce new topics to students or to learn about them yourself.

Stay Curious!