2. Light
• Light is the form of energy visible to
the human eye. This is “radiated by
moving charged particles.”*
• Light provides the energy need for
both plant and animal life. The
plants will then complete the
process of photosynthesis.
• Visible light is the smallest part of
the electromagnetic spectrum.
• The colors of the visible spectrum
change depending on the wave
frequency.
• The higher the frequency the
shorter the wave length is. (see
chart)
*Source: www.centralsquareschools.org/brewerton/artwork/prism.html
3. WAVELENGTH AND ENERGY OF
THE VISIBLE SPECTRUM
COLORS
COLOR WAVELENGTH ENERGY
Red 700 nm 1.771 eV
Reddish orange 650 nm 1.909 eV
Orange 600 nm 2.067 eV
Yellow 580 nm 2.138 eV
Yellowish green 550 nm 2.254 eV
Green 500 nm 2.480 eV
Blue 450 nm 2.765 eV
Violet 400 nm 3.100 eV
Source: Kurt Nassau, Experimenting with Color
4. Color
• “Is a physical phenomenon of light
or visual perception associated with
the various wavelengths in the
visible portion of the
electromagnetic spectrum.”
• White light is made when the
primary colors are added together
“at equal intensities.”
• When looking at objects the object
appears a certain color. This is the
color that is being reflected off of the
object, in reality, the object is every
color but the color is appears to be.
Source: www.centralsquareschools.org/brewerton/artwork/prism.html
5. Prisms
• A Prism is triangular object that separates
white light into the spectrum colors.
• The white light is bent once it enters the
prism, and the prism bends the different
wavelengths of the white light. Out come
the colors of the spectrum.
• The longer the wavelength (red) the less
that it is bent, the shorter the wavelength
(violet) the greater it is bent.
• Prisms are used for many different things:
Spectra Scopes and Binoculars.
• Isaac Newton was the first to show that
“When a second prism brings the
different colors together again, white light
is once more obtained.”
Source: http://www.phy6.org/stargaze/Sun4spec.htm
6. Refraction
• “When a beam of light enters transparent glass, plastic, or water, it usually changes
direction--it bends.”
• Refraction is a phenomenon which occurs with all types of waves in the
electromagnetic spectrum, but is most familiar with light waves. In optics, like
telescopes, the direction of the light is altered by Snell's law. This law is known
as one of the laws of refraction. The other law is when light is being refracted, it
changes direction but stays the the same plane.
• Refraction is what makes it possible for lenses to magnify.
• The speed at which light travels in vacuum is 187,282 miles per second, it slows only a little
bit when traveling through air. Light slows down considerably when it hits a transparent
solid or object.
• Light will not bend when it enters a refractive index.
– Refractive index is when a beam of light enters a surface at a 90 degree angle.
Source: http://centralsquareschools.org/brewerton.artwork/prism.html
7. Reflection
• Reflection is when all of the particles or waves of a beam are
returned when the light reaches a boundary between two
different mediums.
• There are two basic laws that define reflection:
• “(1) that the incident ray, the reflected ray, and the normal
to the reflecting interface at the point of incidence are all
in the same plane
• (2) that the angle of incidence equals the angle of
reflection”
Source: http://www.howstuffworks.com/reflection
8. Refraction and Reflection
Telescopes
Refraction Reflection
Source: The Universe
Refracting telescopes were the
first telescopes ever used. It is said
that two children invented this kind
of telescope, when they were playing
with two lenses. This was perfected
by Galileo. Isaac Newton created
the Reflecting Telescope.
Both telescopes work in the same
way. The difference is that
reflecting telescopes make better
use of mirrors instead of lenses.
9. Hubble Telescope
• The Hubble Space Telescope uses
refection to portray images.
• When light enters the telescope it is
reflected off of large mirrors that are kept
in static, dust free environments. Any dirt
or dust present would ruin the images
collected.
• Then the light passes to a secondary
mirror which reflects the light to the
center of the primary mirror. At the focal
point (where the light is focused into one
point) the light is set to several different
sensors which collect data based on that
light.
• Hubble Space Telescope's “mirrors are
made of glass and coated with layers of
pure aluminum (three-millionths of an
inch thick) and magnesium fluoride (one-
millionth of an inch thick) to make them
reflect visible, infra-red and ultraviolet
light.”
• The mirror can weight almost 2000
pounds.
Source: http://www.howtodostuff.com/hubble
