This is a special class my husband presents during the astronomy class before he begins the talk about more advanced astronomy topics. I'll just be hitting the important topics (because I'm not actually in the class, but keeping the Filthy Little Moose from interfering). Refresh to see the latest. Most recent updates at the bottom.
7:15 Light is in waves. Light is caused by electro-magnetic activity. It has a wavelength. The wavelengths can be very small--on the order of micrometers, and can be very large.
7:20 Visible light wavelengths are about 0.4 micrometers at the violet end to 0.8 micrometers at the red end.
7:25 Combine red, green, and yellow light into white (-ish--depends on the strength of the each flashlight and the 'pureness' of the original light color. Close enough to be convincing.).
7:30 Show white light (from a projector) going through a prism and breaking into its spectrum.
7:35 The wavelength affects how much it is refracted in the prism.
7:40 Whenever light hits anything, some of the light gets reflected, some goes through.
7:43 A diffraction grating has microscopic lines carved into the glass of a mirror. It breaks light into its spectrum more effectively than a prism.
7:45 A prism could be made out of a pan of water tilted.
7:48 When light hits an object, it can be reflected (like a mirror), it can go through the object, or it can be absorbed. Does a demonstration with glass. Scattering also occurs, but that is close to reflection.
7:55 A demonstration of technology that keeps one color of light from going through glass.
8:00 The color of any object you look at is how much light is reflected, absorbed, or transmitted by that object. Put one color object in a different color light and it loses it's color.
8:03 The absorbed light has to 'go' somewhere. It gets changed into a different energy.
8:05 A red object in blue light looks grayish. In a red light it looks very red.
8:07 A white shirt will reflect any color, because the material is made to reflect all colors. A black material absorbs all the visible light and generates more heat from the absorption.
Filthy little Moose has just wondered down the hall. I wonder how long until I get the call to rescue the class from him.
8:10 Color is not IN the object. Color is in the light hitting the object. The wavelength affects how the object appears.
8:15 Moving into the entire electromagnetic spectrum. Much larger than what is visible to humans.
8:20 Smaller wavelengths are ultra-violet, x-ray, and gamma ray. Longer wavelengths include infrared.
Had to remove the babe from the midst of the class.
8:23 Young eyes, generally, are more sensitive than older eyes.
8:25 A digital camera is able to pick up more of the red spectrum than our eyes. They may be able to see an infrared signal that we use, and cannot see, everyday.
8:30 Infrared light is a great way to see warm things. People are a great example (hello, night vision?). Tree leaves radiate infrared radiation at night.
8:34 Pictures representing light wavelengths outside of the visible range are re-colored to represent data to people--those colors are not actual color because they are NOT in the visible light range.
8:36 A dying star might only be visible in the infrared. Jupiter gives off a lot of infrared.
8:38 Radio waves have wavelengths that start at a tenth of a mile and go up to about 60 miles. They are very low energy compared to visible light. Radio waves are NOT sound waves. They are light waves.
8:40 Radio waves are not blocked by the clouds. Radio waves go through walls. Rocks generally reflect radio waves. Demonstration of the reflection of radio waves.
8:43 Technical glitch trying to get the radio to the right station. Ah--all fixed.
8:46 So glad I bought myself a $30 radio transmitter to have my husband steal it and squirrel it away for years on end just so he can find it when it's time to do this particular presentation for the astronomy course. Hmph.
8:50 Lots of questions about what can stop microwaves. Is there some disaster I should know about?
8:53 Radio waves are used in astronomy. They go through clouds so radio astronomer don't have to worry about cloudy nights.
8:57 Cloudy Nights is also my husband's favorite amateur astronomer site.
9:00 Back to ultraviolet. A digital camera also detects ultraviolet better than humans.
9:03 Ultraviolet is so energetic that when it hits some objects, it causes those objects to reflect ultraviolet, but the objects also re-emit different wavelengths--thus changing the color of the object. Fluorescence.
9:08 Great fun showing everyday objects that fluoresce.
9:20 Looking at the sun's ultraviolet light is very interesting.
9:22 Talking about x-rays. NO demonstrations. That makes everyone happy. X-ray wavelengths are very high energy. Black holes give off x-rays.
The Bamm Bamm is still awake. All because I wanted to live blog this!
9:30 And it's over! The students were all troopers.