Objectives

1.   List and explain the properties of light which produce the various optical phenomena common to the atmosphere.
2.   Sketch and label a diagram that illustrates the formation of rainbows and sundogs.
3.   Explain the blue color of the sky and orange/redish sunsets.
4.   Describe and explain the cause of two types of mirages.
5.   Describe the production of the Aurora.

Nature of Light

• reflection - law of reflection
• refraction - “bending” of light as it passes from one medium to another
• dispersion - separation of white light into colors by refraction

Rainbows

• refraction, dispersion, internal reflection of sunlight in raindrops
• primary, secondary rainbows

Raindrop Diagram

Rainbow Diagram

Sky Color

• Why is the sky blue, sun orange?
• scattering - blue light (short wavelength) scattered more than red light (long wavelength)

Mirages

• due to refraction of light as it passes through air of different temperatures (densities)
• vertical temperature gradient
• inferior mirages - air at ground warmer than air aloft
• superior mirages (looming) - air at ground cooler than air aloft

Aurora Borealis (Northern Lights)
Aurora Australis (Southern Lights)

• solar flares emit atomic particles, protons and electrons
• solar wind
• particles captured by earth’s magnetic field and guided towards the poles
• on entering the earth’s atmosphere, collisions between particles and atoms of the atmosphere produce light