Month: March 1998

Why do only certain orbitals exist in an atom?

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Why do only certain orbitals exist in an atom?

Because the electrons in an atom move about as waves, they can follow only certain allowed orbits that we call orbitals. This limitation is equivalent to the case of a violin string—it can only vibrate at certain frequencies. If you try to make a violin string vibrate at the wrong frequency, it won’t do it. That’s because the string vibrates in a wave-like manner and only certain waves fit properly along the strong. Similarly, the electron in an atom “vibrates” in a wave-like manner and only certain waves fit properly around the nucleus.

When an electron hits a neon atom, does it transfer its energy to the atom and l…

Lou Bloomfield Leave a comment

When an electron hits a neon atom, does it transfer its energy to the atom and lose its own forever?

Most of the collisions between an electron and a neon atom are completely elastic—the electron bounces perfectly from the neon atom and retains essentially all of its kinetic energy. But occasionally the electron induces a structural change in the neon atom and transfers some of its energy to the neon atom. In such a case, the electron rebounds weakly and retains only a fraction of its original kinetic energy. The missing energy is left in the neon atom, which usually releases that energy as light.

You said that some rooms in the physics building are made with metal to specific…

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You said that some rooms in the physics building are made with metal to specifically keep electromagnetic waves out. How does that work?

Some experiments are so sensitive to electromagnetic waves that they must be performed inside “Faraday cages”. A Faraday cage is a metal or metal screen box. Its walls conduct electricity and act as mirrors for electromagnetic waves. As long as a wave has a wavelength significantly longer than the largest hole in the walls, that wave will be reflected and will not enter the box. This reflection occurs because the wave’s electric field pushes charges inside the metal walls and causes those charges to accelerate. These accelerating charges redirect (absorb and reemit) the wave in a new direction—a mirror reflection. Just as a box made of metal mirrors will keep light out, a box made with metal walls will keep electromagnetic waves out.

Can microwave ovens leak microwaves? Is my mother’s warning not to stand in fron…

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Can microwave ovens leak microwaves? Is my mother’s warning not to stand in front of the microwave while it’s on valid?

A properly built and maintained microwave oven leaks so little microwave power that you needn’t worry about it. There are also inexpensive leakage testers available that you can use at home for a basic check, or for a more reliable and accurate check—as recommended by both the International Microwave Power Institute (IMPI) and the FDA—you can take your microwave oven to a service shop and have it checked with an FDA certified meter. It’s only if you have dropped the oven or injured its door in some way that you might have cause to worry about standing near it. If it were to leak microwaves, their main effect would be to heat your tissue, so you would feel the leakage.

Is a CB radio also an AM radio?

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Is a CB radio also an AM radio?

CB or citizens band radio refers to some parts of the electromagnetic spectrum that have been set aside for public use. You can operate a CB radio without training and without serious legal constraints, although the power of your transmitted wave is strictly limited. The principal band for CB radio is around 27 MHz and I think that the transmissions use the AM audio encoding scheme. As you talk, the power of your transmission increases and decreases to represent the pressure fluctuations in your voice. The receiving CB radio detects the power fluctuations in the radio wave and moves its speaker accordingly.

What kinds of things get stored in read-only memory, as opposed to storing them …

Lou Bloomfield Leave a comment

What kinds of things get stored in read-only memory, as opposed to storing them on the hard drive?

When you first turn on a typical computer, it must run an initial program that sets up the operating system. This initial program has to run even before the computer is able to interact with its hard drive, so the program must be available at the very instant the computer’s power becomes available. Read-only memory is used for this initial bootup operation. Unlike normal random access memory, which is usually “volatile” and loses its stored information when power is removed, read-only memory retains its information without power. When you turn on the computer, this read-only memory provides the instructions the computer uses to begin loading the operating system from the hard drive.