SCATTERING LIGHT

KEY CONCEPTS

1. Visible radiation is that part of the electromagnetic spectrum that we can see (like the colors of the rainbow).
2. All visible light is part of the electromagnetic spectrum; the radiation corresponding to the color green travels in a certain wavelength, the radiation corresponding to the color blue travels in a different wavelength.
3. White light is visible radiation. It is composed of all the colors of the visible spectrum; the ingredients of white light are red, orange, yellow, green, blue, indigo, and violet. If we were to shine white light through a prism, we could separate white light into its color components (much like the water particles in the atmosphere separate white light to create a rainbow).
4. Particles in the atmosphere such as dust, gas, and aerosols act to either reflect, refract, or even absorb visible radiation. In other words, light is scattered.

MATERIALS

• flashlight
• drinking glass
• eye dropper
• milk
• water
• spoon
• field journal
• (optional) Guide to the planets in our solar system (provided below)

PROCEDURE

CROSS-CURRICULAR IDEAS

• Planetary Science: Nitrogen and oxygen molecules in the Earth's atmosphere, like the milk particles, separate the blue light waves from sunlight. Dust and water vapor within the Earth's atmosphere, just like the milk particles, act to scatter more than just the blue light waves. Therefore, clean and dry air conditions will produce the deepest blue sky color; the blue waves in the light are scattered the most. Nonetheless, Earth has a blue sky because of the oxygen and the nitrogen within the atmosphere. Look at the images of planets provided below. Why is Mars red? Why is Neptune blue? Why is Jupiter orange and red? Are than any other "blue" planets? Much of what we see is due to the components (the gas and the amount of dust) of the atmosphere.
• Physics: What would happen to the colors of an atmosphere if a giant asteroid or meteorite hit the surface of a planet sending dust and water vapor into the atmosphere? How would the color of Earth's atmosphere change? Shine a white light though a dark room, thick with chalk dust (wear a mask). Chalk dust can easily be ascertained by pounding dusty erasers together. What colors do you see?

VOCABULARY

• absorb: to take in and make a part of itself reflect - to throw back or be thrown back, as with light, heat, or sound
• electromagnetic spectrum: the range of wavelengths of radiation created from a system of electric and magnetic fields. Electromagnetic waves emanate from all forms of radiant energy sources including the Sun, the earth, and even light bulbs.
• prism: A optical instrument such as a pyramid of glass. A pyramid has 5 surfaces. When white light is refracted through the first surface within the prism, it is bent to another surface. The light is then reflected back into the air. During the refraction process, the white light is broken up into its constituents wavelengths.
• reflect: to turn or throw backwards off a shiny surface (such as a mirror).
• refract: to deflect or bend through a surface (such as a window).
• scatter: to separate or cause to separate in many directions.
• visible radiation: relatively shortwave radiant energy. Visible radiation is the radiation that our eyes are sensitive (like the colors of the rainbow). This type of radiation is part of the electromagnetic spectrum.

SOURCE

• Adapted from "Winds of Change" educational CD-ROM, Copyright Caltech and NASA/Jet Propulsion Laboratory
• Planetary images and information from "Welcome to the Planets" educational CD-ROM, Copyright Caltech and NASA/Jet Propulsion Laboratory

This photomosaic of the planet Mercury was assembled from individual high-resolution images taken by the Mariner 10 spacecraft shortly before closest approach in 1974. The sun is shining from the right, and the terminator is at about 100 degrees west longitude. Crater basins with extensive plains between craters.

Atmospheric components: trace amounts of hydrogen and helium

The bluish hue of Venus is an effect of the colorization technique used to enhance subtle contrasts in cloud patterns and indicates that this image was taken through a violet filter. Features in the sulfuric acid clouds near the top of the planet's atmosphere are most prominent in violet and ultraviolet light. This image shows the east to west cloud banding and the brighter polar hoods . The features are embedded in winds that flow from east to west at about 370 kph (230 mph).

Atmospheric components: 96% carbon dioxide, 3% nitrogen, 0.1% water vapor

South America appears near the center of this view of Earth. The white, sunlit continent of Antarctica lies near the bottom of the globe. Picturesque weather fronts are visible in the South Atlantic, lower right. This image was taken at about 14:10 UTC on December 11, 1990, when the Jupiter-bound Galileo spacecraft was 2 million km (1.3 million mi) from Earth.

Atmospheric components: 78% nitrogen, 21% oxygen, 1% argon

This mosaic of Mars is similar to the view you would see from a spacecraft. The center of the scene shows the entire Valles Marineris canyon system, over 4000 km (2486 mi) long and up to 7 km (5 mi) deep. It extends from Noctis Labyrinthus, the arcuate system of graben on the west side, to the chaotic terrain on the east side. Many ancient river channels begin from the chaotic terrain and north-central canyons and run north. Three Tharsis volcanoes are visible to the west (dark red spots). They rise 10 to 18 km (6 to 11 mi) above the Tharsis Plateau, attaining elevations of 18 to 26 km (11 to 16 mi).

Atmospheric components: 95% carbon dioxide, 3% nitrogen, 1.6% argon

Jupiter is a "gas giant"; all gas giants are similar to Jupiter in composition. Jupiter's diameter is 11 times Earth's diameter and 20% larger than Saturn's, making it the largest planet in the solar system. Gas giants are also very much larger than terrestrial ("rocky") planets. This color-enhanced image of Jupiter was taken by the Voyager 1 spacecraft.

Atmospheric components: 90% hydrogen, 10% helium, .07% methane

Several dark spoke-like features can be seen across the broad B ring (left of planet). The moons Rhea and Dione appear as dots below and below left of Saturn, respectively. This photo was taken July 21, 1981, when the Voyager 2 spacecraft was 33.9 million km (21 million mi) from the planet. Voyager 2 made its closest approach to Saturn on August 25, 1981.

Atmospheric components: 97% hydrogen, 3% helium, .05% methane

The greenish color of Uranus' atmosphere is due to methane and high-altitude photochemical smog. The Voyager 2 spacecraft acquired this view of the seventh planet while departing the Uranian system in late January 1986. This image looks at the planet approximately along its rotational pole.

Atmospheric components: .83% hydrogen, 15% helium, 2% methane (at depth)

On its approach to Neptune in August 1989, the Voyager 2 spacecraft captured this image of the fourth and outermost of the giant gas planets. This image shows two of the four oval cloud features tracked by the cameras. The large dark oval near the left edge revolves around Neptune every 18 hours. The bright clouds immediately to the south and east of this oval substantially change their appearance in periods as short as 4 hours. The second dark spot, at lower right edge, revolves around Neptune every 16 hours.

Atmospheric components: 74% hydrogen, 25% helium, 1% methane (at depth)

Atmospheric components: methane and nitrogen ??