Recent content by kbar1

Very sorry about that. I was just trying to help. Silly me, that should be cos^2(60°). But why is 3I0/16 incorrect? Intensity is reduced by 1/2 after the first screen, another 1/2 because of the second screen, and by cos^2(30°). So that would be 3I0/16. Am I missing anything? And why is...

If the intensity of the light before entering the first screen is I_{0}, then its intensity after exiting the screen in the middle is \displaystyle\frac{3I_{0}}{16}. By passing through the third screen, intensity will be reduced further to cos^2(70)...

Hello! The rod's center is stationary. The two ends are rotating. But I think I got your point. That has to be one of the quickest problem resolutions ever! Thanks a lot!

Homework Statement Q: A rod of length l rotates with a uniform angular velocity ω about the axis passing through its center and perpendicular to its length. A uniform magnetic field B exists with its direction normal to the plane of rotation. The e.m.f. induced between the center and anyone...

A 10 gigatesla field ... would be lethal even at a distance of 1000 km, tearing tissues due to the diamagnetism of water. At a distance halfway to the moon ... could strip information from the magnetic stripes of all credit cards on Earth. From [en.wikipedia.org].

Guess that clears it. Thanks all.

According to special relativity, velocity cannot be added to another velocity linearly. But I was thinking, what about kinetic energy? K.E. = mv2/2. As velocity increases, the object's mass also increases. The way I see it, the increase in mass "compensates" for the less-than-expected increase...

Never thought about it. Does the electric field set up between the plates oppose the insertion of the dielectric? Wild guess on my part: The energy is used to attract the dielectric, because the capacitor system with it has lesser energy (i.e. more preferable) than the capacitor without the...

Pardon me if I'm wrong (I'm new to this topic), but does the force applied to push the dielectric matter? The only thing nagging me is that the energy stored in the two cases is different, and I'd like to know where the difference went.

Suppose a (parallel plate) capacitor of capacitance C is charged to a potential difference V and then disconnected and isolated. Energy stored E1= Q2/2C. Now if a material of appropriate dimensions and dielectric constant K is fully inserted between the plates, energy stored E2= Q2/2KC. E2...

I'm confused. I thought that the combination of large mass and strong magnetic field allowed Earth to mostly retain its atmosphere. Mars, being less massive and having a weak magnetic field, had its early atmosphere stripped [science.nasa.gov]. But then why does Venus (with no appreciable...

You mean it gets red shifted? [en.wikipedia.org]. Speed is the same I believe, unless you run it through anything other than vacuum/air.

What's the current hypothesis as to what happens when the black holes become too small to exist?

Also, if situated in larger distances, wouldn't the gas giants act as "guardian angels", taking care of many stray asteroids or comets that would otherwise *might* crash into planets with life?

That is what Hawking thought, I think. A black hole (if we assume that it doesn't have a temperature, i.e. doesn't emit energy) violates the second law of thermodynamics, by sucking up everything that falls on it (reducing the entropy of the universe), but doesn't compensate for it (by emitting...