Recent content by aresnick

Right, it still depends on the positioning of the light. Check out the Wikipedia page on lenses, all the diagrams you're looking for can be found there.

Yep, you can use the concave mirror as a collector and the convex lens to focus the light. So if you take a look at the lensmaker's equation, you can apply that repeatedly to predict the focal length (which is where you want the stage to be if you're looking for a tightly controlled spot)...

I believe that the transmitter controls what's essentially an amplifier (either via op-amp or transistor), controlling the size of the voltage sent to the motor. So I believe fixed pitch helicopters can't actually roll unless they have extra ailerons; without ailerons, the torque control is...

The voltage in a battery is a function of the chemistry within it. In a wet cell, for instance, the electrolytes used (say, lead and sulfuric acid) determine the voltage produced (as characterized by the "standard electrode potential"). The output current is a function of the internal...

I remember looking for this about a year ago. After searching extensively, I came across a site claiming that this was a special font developed for the purpose of the book. Whether or not I believe it, after a couple days of searching, I hadn't found anything, so I ended up using the fcursive...

As I understand it, with a Fixed Pitch the angle of the main blades remains constant and the flyer controls altitude by using the speed of the main motor, simply creating more or less lift by choosing the attitude of the helicopter (which determines how much of the lift propels the helicopter...

So I don't think Radio Shack sells these, but you can purchase photodiodes or phototransistors with coatings that select for certain wavelengths. With that, a battery, and a resistor, you should be able to hook up an LED between them, and when IR hits the photo{diode,transistor}, current flows...

If you check out the Wikipedia page on stage lighting instruments, you'll find a couple links to the primary classes of spotlights: ellipsoid reflectors and Fresnel lens spotlights. The ellipsoid reflectors are more common, and often have a barrel and gate providing for an iris that let's you...

Sounds good =) Luminol is actually pretty cool to play around with: the iron in your blood catalyzes its oxidation. I don't actually know what they spray on prior to using the UV light, as I was under the impression that UV-B rays would cause blood to fluoresce, naturally.

I think we need a bit more information, first. So, if a ray of light enters the very center of a lens, it will pass straight through, unbent. If the source point is beyond the focal point of the lens, the light rays will tend to bend toward the center of the lens, and if it the source point is...

But I'm suggesting that the smallest set that contains A_{1} \ldots A_{k} is simply a set containing \left\{A_{1} \ldots A_{k}\right\} and the empty set (since every set must contain the empty set). It just seemed like a very simple object, in that case. Does that make sense?

Homework Statement Let \mathscr{X} be a set, \mathscr{F} a \sigma-field of subsets of S, and \mu a probability measure on \mathscr{F}. Suppose that A_{1},\ldots,A_{n} are independent sets belonging to \mathscr{F}. Let \mathscr{F}_{k} be the smallest subfield of \mathscr{F} containing A_{1}...