Recent content by alanf

Thank everyone. I knew that the mirror had to pick up some energy from the light. It was kind of an odd question to put on the final, since the prof had made an effort in lectures to point out that reflective objects are under twice the radiation pressure of absorptive objects.

On my E&M final, a question asked 1) how much energy a light beam transferred to a non-reflective object in x seconds (3 joules), 2) what pressure the light exerted on the object during that time, and 3) what energy would be transferred to a perfectly reflective mirror by the same beam of light...

Thanks Andy. So it sounds like I need to read up on wave retarders. I'll take a look at the plastic again later today.

I finished my online E&M class today, and the prof told us to experiment with polarizers. While doing that, I found this: I put a piece of plastic between two polarizers, and found that at a certain angle between the two polarizers, a portion - though not all - of the plastic darkened. So I...

Thanks to both of you for your replies. I'll look through the text posted by BvU, but in the meantime, I am still very puzzled by one thing. If the solenoid was simply straight, and not curved into a toroid, B at the center would be 12.86 T, right? If so, I'm really surprised that curving it...

Homework Statement Take a steel core (K_m = 2500) electromagnet, bend it into a loop with a small air gap, and determine the B field in the gap. The cross-sectional area of the toroid is 4cm^2, and the air gap is 2.5mm. The current through the coil's 120 turns is 15 amps. The radius of the...

Thanks, ehild. That was a very clear and helpful explanation.

Homework Statement I'm working my way through MIT 8.02x, the intro E&M course, on EdX. In Homework 3/Problem 3, we insert a dielectric between plates in a capacitor that is connected to a battery supplying potential V. So the charge on the capacitor increases by Q. How much work is done by...

Thanks for your very clear answer (and sorry for being so late to reply). I think I have a better grasp of the geometry of the charge arrangement now.

I'm working my way through MIT 8.02x on EdX (an archived course, so it's a bit lonely in there right now!). The problem statement: Two spherical conductors, A and B, are placed in vacuum. A has a radius rA=25 cm and B of rB=35 cm. The distance between the centers of the two spheres is d=225...

So to take the easier case - the interferometer with widely differing arm lengths - no interference, because we could easily determine the path the photon took with a simple stopwatch? What prevents us from doing the same with the double slit experiment? Of course we'd need something more...

Thanks Misericorde. So to go back to the double slit experiment, what is it that prevents us from measuring the flight time of the photon, and thus determining which slit it went through (assuming the source-slit-detector distance is not precisely the same for each slit), and destroying the...

That's a clever experiment, one which I've never seen described in any of the lay discussions of the subject. So you don't actually have to check the polarity of the arriving photon. It's enough simply that you *could* check? So how can the double slit experiment work? Is there some quantum...

Hi Dr. C! I only brought up the double slit experiment because the issue seems similar to me. If the slits aren't the same distance from the light source, simply by measuring the time from emission to detection, an observer should be able to determine which slit - and similarly, which arm of...

One arm of a Michelson interferometer is one light second long, the other is one light minute long. We run photons through it one at a time. Do we see interference? And if so, when? After one second? One minute? Some other time? I've been reading a number (too many!) "layman's" books on...