AND COLORS -
AUGUST 05, 2003
is the mother of all curves, curved?
are formed when rays of sunlight enter rain drops and get reflected
internally. These rays exit the drop, making roughly a 42 degree angle with
the incident rays. Upon entering the rain drop, sunlight, which is white,
separates into the different colors of the spectrum. This happens because
each color has a different wavelength, and gets bent differently by the rain
drop due to refraction. The ray leaves the drops as separate colors.
be able to see a rainbow, an observer must look at the perfect angle to
capture the rays that leave the rain drops after refraction and internal
reflection. If the sunlight entering the drops is parallel to the ground,
then the observer would have to look at roughly a 42 degree angle to see the
colored light leaving the drops. The set of all the drops that have the
perfect angle with the sun and with the observer will form a curve in the
sky. See this figure
to better understand the physics behind the curved shape.
Discs also display rainbow colors. But the science governing the colors
visible on the CD surface is quite different. The slots etched on the
surface of the CD form a convenient diffraction
grating. Diffraction of white light at those slots causes separation of colors,
again due to the difference in wavelengths. What colors are seen on the CD
surface depends on the angle of the incident light and the angle of
observation. Constructive and destructive interference between different
diffracted paths determines the observed colors and patterns.
:: :: ::
picture shows an interesting color pattern I captured on a CD. It is my
entry for this week's Photo