Station 1 Projecting Visible Spectra (setting direction)
Objective: To study the range of colors in the visible spectrum.
Procedure:
1. Make a partition with a narrow slot in its center to block all but a narrow beam
from the flashlight.
2. Cut out a 4 by 1-centimeter vertical rectangle out from a 10 by 10 centimeter
piece of poster board.
3. Tape the two single-edge razor blades to the poster board so that their edges
face each other and the reis a 1- to 2-millimeter gap between them.
4. Darken the classroom (the darker the better).
5. Brace the partition so that it stands up right with the gap in the vertical direction.
6. Aim the flashlight beam at the screen and focus it into a tight beam. Direct the
beam of the flashlight directly through the gap in the partition so that a narrow
vertical slot of light falls on the screen.
7. Stand the glass prism upright and place it in the narrow beam of light on the
opposite side of the partition.
8. Slowly rotate the prism until the narrow slot of light disperses the visible
spectrum. Depending upon the exact alignment, the spectrum may fall on a wall
rather than on the screen. Adjust the setup so that the spectrum is displayed on
the projection screen.
Background: Visible light, passing through a prism at a suitable angle, is dispersed into its
component colors. This happens because of refraction. When visible light waves cross an
interface between two media of different densities (such as from air into glass) at an
angle other than 90 degrees, the light waves are bent (refracted).Different wavelengths of
visible light are bent different amounts and this causes them to be dispersed into a
continuum of colors. (See diagram.)