Manual

3
Color of filter used →
Color of plate in white
light ↓
W R M O Y G C B V
R
M
O
Y
G
C
V
Index: W-White, R-Red, M-Magenta, O-Orange, Y-Yellow, G-Green, C-Cyan, B-Blue, V-Violet
• After familiarizing yourself with the different colors, perform some experiments on your own by
observing a color card illuminated by light of one color and viewed in another color. Try to predict
your observation before performing the experiment.
Color Combinations: By using the side-openings, up to three colors can be projected onto the screen.
Place the weakest color filter in the center-aperture and the stronger ones on the sides so that intensity
loss (due to reflection) is compensated.
Initially, take any set of filters and note down the different colors formed by their overlapping.
Next, try to find COMPLEMENTARY COLORS, i.e., combinations that reproduce white light. Note
down the colors and their complement (the complement of color A is the color, which on combining
with it gives white light).
Shadows: Remove the filters and close the side-openings. Place a pencil in front of the screen. A sharp
shadow within a faint one can be observed. If the faint shadow is too faint, use a tracing-paper to
diffuse the light coming from the light box.
The sharp shadow is called the UMBRA and is the region where no light falls. The faint shadow
enclosing the umbra is the PENUMBRA, the region where partial light falls.
The phenomenon of umbra-penumbra can also be observed in everyday-life in your own shadow.
Try to explain the phenomenon with a ray diagram.
Colored Shadows: Place a set of complementary colors in the openings and adjust the mirrors to
obtain the white light on the screen. Place a pencil in a patch illuminated by all three colors and
observe the shadows formed. Shift the pencil to patches illuminated by all three colors and observe the
shadows formed. Shift the pencil to patches illuminated by two colors and then by one color and
observe the shadows. The number of shadows formed is the same as the colors illuminating the patch,
while their colors are the same as a few of the patches.
The above phenomena occur with any set of colors (not necessarily complementary). Try to explain the
number of shadows and their colors. (A ray diagram will prove helpful here, too.)
Experiments on Reflection:
Reflection is a phenomenon where light falling on a surface bounces back, in accordance with the
following laws:
1. The angle of reflection is equal to the angle of incidence.