Recent content by Tranceform

Yes. Well, I have never seen a radiometer IRL, so from what direction is the light shining on it? If it's put in such a direction that equally many photons hit both shiny and black side, I would assume it would rotate from shiny to black. Ok, that makes sense. But strangely in my book that is...

Homework Statement The photograph shows a device called a radiometer. The four regular panels are black on one side and shiny like a mirror on the other side. In bright light, the panel arrangement spins around in a direction from the black side of a panel toward the shiny side. Do photon...

It's true I think of the "re-emitting" as reflection, are you saying this view is incorrect? How can then one think of it, how is it different from reflection? So if I understand it correctly (please correct me if I'm wrong) when we have electromagnetic radiation shining on a perfect...

But what does it mean it has been "lost"? Where did it go? Ok, I understand the emitted radiation depends on temperature. But then I have some follow-up questions: 6) Under which circumstances does a perfect blackbody re-emit all incident radiation? 7) Is the absorbed energy of a perfect...

Thanks for clarifying!

While dot product could be viewed as "how much a vector is parallell to another vector", the cross product could be viewed "how much a vector is perpendicular to another vector". To me it is easiest to understand it physically by looking at Torque. With torque you can really see that "the more...

Is this analogy in reference to question a) or b)? I thought this analogy didn't apply for light? Suppose for example that you instead of throwing a ball shined a flashlight, the speed of light postulate says that I wouldn't see this light as c+2m/s even though you are moving but I would still...

The following text is an excerpt from a physics book: I find this paragraph a bit hard to grasp, so I have some questions about it and I would appreciate if they are clarified. 1) What is meant by "the energy carried off by the radiated electromagnetic waves"? As I interpret this it means...

Homework Statement An intergalactic cruiser is approaching a hostile spacecraft . Both vehicles move at a constant velocity. The velocity of the cruiser relative to the spacecraft is vCS=+0.7c, the direction to the right being the positive direction. The cruiser fires a beam of laser light...

Your second reply is much better and more explanatory but I'm still wondering something. I wonder why you use words like "obviously" unless you clarify what is so obvious about it? I have looked in two different physics books where this derivation is done and in both cases they use binomal...

This unfortunately doesn't answer my question. Whether the derivation is made using binomal expansion or Taylor expansion doesn't answer my question. The question is rather: why would you do (again I'm not looking for a mathematical but physical reason) any expansion - of a seemingly constant...

The kinetic energy of an object can be expressed as KE=mc^2(\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}-1) (1) For speeds much lower than the speed of light however, we know that KE=\frac{1}{2}mv^2 (2) The second expression can be derived from the first one using binomial expansion of the term with the...

Proper time between the two events. I guess then that since the events take place at the same place, the proper time is measured according to an observer inertial for those two places, which would be a stationary observer. However if the time measured would have been only on the baseball going...

Ok, I reposted it: https://www.physicsforums.com/showthread.php?p=4798201

Homework Statement A baseball player at home plate hits a pop fly straight up (the beginning event) that is caught by the catcher at home plate (the ending event). Which one or more of the following obeservers record(s) the proper time interval between the two events? (a) A spectator sitting...