Do You Know
Questions & Answers on General Knowledge.
How does a sound dish work? I know that it's a parabola, but I can only find drawings not explanations.
A sound dish is actually a mirror telescope for sound. When sound waves from a distant source encounter a rigid parabolic surface, they reflect in such a way that they focus to a point. If you put a microphone at that point, it will detect the sound waves from the distant source. You can see this focusing effect by drawing a parabola on a sheet of paper and directing parallel lines—the sound waves from the distant source—toward the parabola. If you reflect each line in a mirror-like fashion from the surface it hits, you'll find that all the reflected lines pass through a single point as they move away from the parabola.
How does a steam heating system work?
What is hell?
Given a lever long enough, could you move the world?
Why does a fluorescent bulb sometimes appear blue, especially right before it burns out?
How did the Second World War end?
Why do scantron-type tests only read #2 pencils? Can other pencils work?
Are water plants always good for the pond?
How deep under water can I go while breathing from a hose that rises above the surface of the water?
Do songbirds have to learn from their parents how to sing?
How are the days of the week named?
How do plants live in a desert?
How big are Saturn's rings?
How do phosphors change the light from ultraviolet to visible?
How did the centre of world commerce, Wall Street, get its name?
How does a halogen bulb work and is it really better than a regular bulb?
What gives Uranus and Neptune their blue colour?
Who were the Vikings of Scandinavia?
What languages are spoken in Europe?
How far is the Sun from us?
How does a regular lamp (light bulb) work?
Why is it said that something with proven quality has passed the “acid test”?
What was Renaissance literature about?
Which insect is sometimes called a "vicious predator"?
What do sea lions eat?
How does a parabolic microphone work?
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