Visible Light Spectrum

Britney KoetsierNicole Podnecky

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

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 eVSource: Kurt Nassau, Experimenting with Color

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

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

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

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

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.

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

Source: The Universe, and www.nasa.org

Examples of Visible Light