In a ripple tank, why are the crests represented as bright areas and troughs as dark areas?
548722
This is an effect of concavity/convexity and overhead light.  The crest of a wave is convex, and acts as a concentrating lens, meaning that the light that falls onto the crest is, on average, redirected toward the area underneath the apex of the wave, making that area brighter.  The trough is convex, and acts as a dispersing lens, meaning that light that falls into the trough is, on average, redirected away from the area underneath the trough, making that area dimmer.
868733
Basically as everyone suggests it is to do with magnetism. when electrical items are operated they generate electrical fields that in turn have magnetic fields. the same can be said for fixed magnets. These fields bend the "beams" within the CRT and illuminate the wrong phosphors. such a phenomenon Displays as a purple pink (usually) or red patch on the screen. The degauss coil you operate when you push the button generates a small localized magnetic field of its own which slowly dissipates as electrons through the components within the circuit thus restoring the CRT's normal magnetic field, resulting in the proper phosphors within the CRT being excited rectifying colour problems on the display
424768
It looks like that because of the refraction of light through moisture in the atmosphere. What you are seeing is really just water in our atmosphere difusing the sunlight reflected by the moon.
288720
Vegetation emits in the infrared wavelength.  On false-color infrared mosaics, vegetation appears in red instead of green. The "redness" indicates vegetation density, type and whether growing on dry land or in a swamp. Grasslands appear light red, deciduous trees and croplands appear red, and coniferous forests appear dark red or maroon. Desert areas appear white and urban areas appear bluish green. Lakes, rivers and oceans appear in various shades of blue, dark blue for deep water and light blue for shallow or turbid water
539515
Moses and Campbelp have it right--the fluorescent light is closer and of larger apparent size (especially if it is a long tube!).  The sun's shadows are not perfectly sharp because it has some size.  This is the cause of the "penumbral" lunar eclipse, when the moon dims but is not fully eclipsed, as it passes through the dim but not dark portion of the Earth's shadow (the penumbra--the darkest part of a shadow is the umbra).
492244
I think I heard this answered before somewhere. If I remember corretly it's that the amount of coloured pigment in the soap is tiny. When 'foamed up' the actual foam is only a few microns thick...so thin that the colour pigment (which was a small % in the first place) can't be seen?
294598
For the same reason that uncurtained windows of a house bathed in sunlight look darker than the rest of the house. The light goes further inside, so a greater proportion of it is diffused and absorbed internally, and less is reflected back out. The water acts as a light pipe, which you can demonstrate by holding a sheet of thin paper with a wet spot up to the light. The ref. provides a fuller explanation.
776710
they make colors usually white stand out more. if you have glow in the dark stuff it will make that stand out too
821271
Because there is a "serrated" surface embedded in the print that defracts the light and scatters it into its different components.  The principal is the same as a Prism.  Visible light is made of many colors, from blue to red and if you put white light into a prism it will separate it into the many colors of the rainbow.  The reason you can see the different colors on the seal is because when you move the bill around, you are looking from different angles and seeing that particular frequency of the light spectrum
555902
They are water droplets. Huge amount of them will be able to partially block sunlight. So, we see them as being black.
703428
It used to be like that with fluorescent lights only, but not anymore.  See this article.\n\nhttp://www.eweb.org/business/energy/energysmart/ebd/9811/lighting_myth.htm
1114373
When two waves of the same wavelength are 180 degrees out of phase, they will destructively interfere with eachother.\n\nWhen the crest of one wave means the trough of another wave (180 degrees, 1/2 cycle, apart), they cancel out.\nYou are left with noting.\n\nhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l1b.html
780823
Could be a strange mirage. Sometimes weird mirage can project skyline of cities beyond horizon or just strange shapes in sky when atmosphere refract lights in unusual ways.
1025185
ripples are just a propagation of energy. Some energy source started the ripples.
1153958
You're obviously not looking hard enough!  After it's been raining (not this week) and the sun is coming out again, look at a cloud, a dark one is better than a light one, and you should be able to see how the edge of the cloud appears to be lined with silver
1025274
Did you try changing the color of the font and/or background?\nMay need to try a couple of times to select the right thing, since you can't easily tell where the edges are, but maybe the text is in a color that matches the shading in that area.
841832
Robertmca has given you a good description. But you may perhaps mean what is correct: fullscap or foolscap - and why is it so called?\nIt is foolscap. It is called foolscap because, in days gone by, there used to be a  'water mark' on the paper which could be seen if the paper was held up to the light. The mark was the shape of a dunce's cap - or fool's cap.