Hot and Humid and rainbows explained
This morning it is partly cloudy with a chance of a thunderstorm and a chance of rain in the afternoon. High of 84F. Winds from the SSW at 5 to 10 mph. Chance of rain 20%.
Tonight it will be partly cloudy. Fog overnight. Low of 64F. Winds less than 5 mph.
The readings from my own instruments are:
The humidity is 69% with a Dew Point of 57ºF and temp is 72.5ºF.
Our wind direction is Southeast between 1.4 MPH and 2.0 MPH.
Our Barometric pressure is 30.32 HPA 1016 and falling with a weather graphic indicating rain.
The UV rating is 1 out of 16, Sunrise is 4:58 a.m. sunset is 8:26 PM and Moon Rise is at 8:15 a.m. EDT and the moon phase is waxing crescent.
For the pilots out there, Raw Metar readings are:
METAR KAUG 301053Z AUTO 20003KT 10SM CLR 17/14 A3000 RMK AO2 SLP160 T01670139
Visibility is 10.0 miles/16.1 kilometers with some cotton-ball clouds here and there.
We received no rain here in the past 24 hours.
Speaking of rain, when it rains, and then stops, what causes a rainbow?
You know that light is made up of a collection of many colors: red, orange, yellow, green, blue, indigo, violet. That is why a prism can take in white light on one side and produce its own mini-rainbow on the other side. To understand rainbows, you have to start by understanding what is happening inside a prism to let it separate white light into its colors.
A prism is a triangular piece of glass or plastic. To get it to produce a mini-rainbow, you allow a narrow strip of white light to fall on one face of the triangle, like this: (Image not shown here)
The dispersion of colors in a prism occurs because of something called the refractive index of the glass. Every material has a different refractive index. When light enters a material (for example, when light traveling through the air enters the glass of a prism), the difference in the refractive index of air and glass causes the light to bend. The angle of bending is different for different wavelengths of light. As the white light moves through the two faces of the prism, the different colors bend different amounts and in doing so spread out into a rainbow.
In a rainbow, raindrops in the air act as tiny prisms. Light enters the raindrop, reflects off of the side of the drop and exits. In the process, it is broken into a spectrum just like it is a triangular glass prism, like this: (Image not shown here)
between the ray of light coming in and the ray coming out of the drops is 42 degrees for red and 40 degrees for violet. You can see in this diagram that the angles cause different colors from different drops to reach your eye, forming a circular rim of color in the sky -- a rainbow! In a double rainbow, the second bow is produced because droplets can have two reflections internally and get the same effect. The droplets have to be the right size to get two reflections to work.
The next time you spot a rainbow, you will see it in a whole new light.
Downloaded in whole from: HowStuffWorks.com. <http://science.howstuffworks.com/nature/climate-weather/atmospheric/question41.htm>
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