The Spectrum of White Light

Aims:

· Put the arrangement (as shown above) together on the guide rail but leave out the prism and put the white screen on the guide rail. Use the lens to focus the picture of the gap on the white screen.

· Put the prism on the guide rail as shown above. The picture of the gap is being deflected now (Why?). Therefore the white screen has to be placed aside from the guide rail. Try to find the best position for it. Rotate the prism until the spectrum is pure.

· Look at the deflected picture of the gap. What can you see? Which colour undergoes minimum, which colour maximum deflection?

· Connect the IR-sensor to the oscilloscope using a wire. Take the IR-sensor and move it along the visible spectrum. Watch the intensity of the measured signal (higher intensity Þ higher line). Test if there is any intensity beside (left or right) the visible spectrum. Where is the maximum of intensity? What does this mean?

· White light is a compound of all colours of the rainbow (spectrum). Therefore it must be possible to gain white light by putting together all the colours of the spectrum by a lens. Test if this is right, by putting together the arrangement sketched above.

List of Materials:

· one lamp (with current source) · two pieces of cardboard · one lens (f = 10 cm) (with holder) · one lens (f = 5 cm) (with holder) · one IR-sensor

· one prism (with holder) · one guide rail · one white screen (with holder) · one oscilloscope (with connecting wire)