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 re
ctangle out from a 10 by 10 cen
timeter
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 betwee
n them.
4.
Darken th
e classroom (the darker the bet
ter).
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 th
rough 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. Ad
just the setup so that the spec
trum is displayed on
the projection screen