ingridscience

Download from the Exploratorium site. Their instructions follow.

1.Leave the cap on the bottle, but peel off the label.
2.Count down about three ridges (or about three inches) from the top of the bottle. Using a scissors (or a utility knife, if an adult is doing this), cut along the ridge. Make sure you cut evenly along the edges. Trim off any bumpy ridges.
3.Recycle the bottom of the bottle; you’ll be working with the top half.
4.Take your hole punch and punch a hole as far up from the bottom of this piece as you can go. Put the straw through the hole to test the size. It should be a tight fit. If the hole isn’t large enough for the diameter of the straw, repunch the hole in nearly the same spot, making it slightly larger.
5.Cut the fingers off the glove. The glove should now look like a wide tube.
6.Cut the tube open to form a sheet of pliable material, or a membrane.
7.Stretch the membrane over the opening at the bottom of the bottle, making sure the hole- punched hole on the side isn’t hidden by the excess material.
8.Attach the membrane to the bottle with a rubber band. Wrap the rubber band around the bottle several times, making sure that the membrane’s taut.
9.Twist the top off the bottle.
10. Roll a piece of construction paper into a tube on a flat surface. Make the tube as tight and as straight as possible.
11. Put the rolled tube into the large open hole on the bottle where the cap had been. Let go of the tube when it barely touches the bottom of the membrane. It should fit securely in the hole.
12. Insert the straw in the hole on the side of the bottle and blow into the straw; your water bottle saxophone should play!
13. Tape the paper tube so it stays in place.
14. To make different sounds, add finger holes. To do this, pinch the paper tube slightly and cut out a diamond shape; repeat to make more finger holes.

Distribute materials to make rainbows, either with one or several methods. These methods separate light into its colours.
White light is a mixture of all the colours. Coloured lights are made up of a mixture of a subset of these colours.

CDs/DVDs:
Tip the disc towards the room lights, the sun, or shine a flashlight on them. When light hits the groves in the CD, they spread the light out into its component colours, which line up into a rainbow.

Cut glass or prisms:
A piece of cut glass or a prism in a box can be arranged so that a flashlight or the sun shining onto a cut edge of the glass separates the colours of the white light into the colours of the rainbow.
A hanging ornament (sometimes called a "rainbow catcher") of cut glass separates light into its rainbow of colours.
As the light goes through the glass it is bent - different colours bend by different amounts so are separated out.

Scratched plastic/diffraction gratings/rainbow glasses:
The scratched lines in the plastic of these materials separate light into its component colours.
As the light goes through the plastic it is bent - different colours bend by different amounts so are separated out.

White light separates into the spectrum of the rainbow. With objects or light sources that only emit some colours e.g. holiday lights or various coloured objects, they only emit a portion of the whole colour spectrum, so when their light is separated, a reduced range of colours are seen.
(Astronomy connection lesson plan on star spectra.)

Using marker pens, the scratched plastic can be used to find out the primary colours of light (cyan (a light blue), magenta (pinky red) and yellow:
Give students purple or dark blue, green and red markers. Ask them to make a blob of colour on white paper, then look at the blob to see what colours "bleed" out of the sides. They should find that cyan, magenta and yellow appear around many colours. This is because the scratched plastic is splitting up the light coming from the marker pen and splitting it into its component colours - these are the colours that make up light (cyan, magenta and yellow). Just like paint there are also secondary colours, which might be seen where primary colours overlap.

Oil:
A thin layer of oil (e.g. on the road from a car) can also make a rainbow of colours when light from the sun hits it.

With older students, discussion can include how the colours are separated:
The edge of a glass prism, or cut glass, bends each of the wavelengths (colours) of light slightly differently, so that they are separated out. The bending of light is called refraction.
The colours in a CD or scratched plastic, in bubbles or an oil slick are formed by interference. When light is reflected from the grooves of the CD or the top and bottom surfaces of a bubble or oil, the light waves interact with each other. Interference of the waves enhances some wavelengths and cancels others in different places, resulting in a rainbow.