Copyright © 2013 Pearson Education, Inc. The Atmosphere: An Introduction to Meteorology, 12 th Lutgens Tarbuck Lectures by: Heather Gallacher, Cleveland State University Chapter 16: Optical Phenomena of the Atmosphere Copyright © 2013 Pearson Education, Inc. Modified by AJ Allred for Salt Lake Community College Meteorology 1010 Fall, 2013
Copyright © 2013 Pearson Education, Inc. Dear Students: If you study this PowerPoint a little bit, you will find that everything comes down to just a simple concept: Our eyes detect the visible portion of the solar electromagnetic spectrum. Sunlight comes in various wavelengths that travel at different speeds. Rays of sunlight are broken into different colors by striking air and water vapor. All of the phenomena in Chapter 16 are based on this simple idea. Try it. The final exam will be easier if you do.
Copyright © 2013 Pearson Education, Inc. Light rays tend to bounce off at the same angle they came in This is why carpet and grass have little reflection – light rays are scattered all over because the bounce surface is rough.
Copyright © 2013 Pearson Education, Inc. Interactions of Light and Matter Refraction is the change of direction of light as it passes obliquely from one substance to another. It can also bend light – or reflect it, or absorb it. Various wave lengths of solar energy and visible light travel at different speeds and respond differently when passing from air to water. Air is sometimes thin (hot air) or dense (cold air) dry Air is either dry or humid. So, with temperature and humidity differences, light bends, reflects, or absorbs differently, creating strange and interesting visual effects in the sky. Key issues for the examples that follow.
Copyright © 2013 Pearson Education, Inc. Interactions of Light and Matter The toy car changes direction when its wheels run across a substance with more ‘friction’ Light changes speed and direction on striking something more solid
Copyright © 2013 Pearson Education, Inc. Mirages Hot air near the surface bends light differently than cooler air aloft. Notice that the observer’s brain believes that the object is found back along the apparent track. In reality, the track is bent, and comes from elsewhere. Brain path
Copyright © 2013 Pearson Education, Inc. Mirages Cooler air bends light differently than warmer air. The observer’s brain suggests that the image is located along the apparent track that is reaching her eyes. In reality, the ‘track’ is bent, and comes from somewhere else.
Copyright © 2013 Pearson Education, Inc. A rainbow appears as an arch-shaped array of colors in the sky. Water vapor in the sky breaks sunlight into its various parts (colors) because different wave lengths travel at different speed. Each different wave length of color is either absorbed or passes through, depending on how they hit water droplets.
Copyright © 2013 Pearson Education, Inc. Rainbows Each water droplet has its own effect on sunlight passing through.
Copyright © 2013 Pearson Education, Inc. Halos, Sun Dogs, and Sun Pillars
Copyright © 2013 Pearson Education, Inc. Halos, Sun Dogs, and Sun Pillars
Copyright © 2013 Pearson Education, Inc. Halos, Sun Dogs, and Sun Pillars At various extreme angles, such as at sunset or sunrise, sunlight passes through more atmosphere. Some colors are totally absorbed, while the red/orange ones tend to get through. During the day, blue gets through easily, so the sky is blue.
Copyright © 2013 Pearson Education, Inc. Glories Notice the colored arcs around the object. Objects bend light that passes nearby. Bending/refrac ting causes various wave lengths of color to act differently
Copyright © 2013 Pearson Education, Inc. Coronas Appears as a bright white disk centered on the Sun or Moon.
Copyright © 2013 Pearson Education, Inc. Irridescence is caused by sunlight passing through water vapor and air at different angles. Each different wave length of color reacts differently to refraction. Some colors are almost totally absorbed or reflected. Other colors go through at various angles.