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1

One way to think of this is to imagine a high-speed camera which takes 1000 frames per second (which is 40x as many as a regular film camera). Then imagine putting the frames into groups of 40, and averaging each group, so that you now have a film with a normal framerate, where each frame is the average of 40 high speed frames. The resulting film would be ...


2

The answer is that your view or sight is different from the bare images made by the imaging optics of your eye on your retina. A "view" also includes signal processing from the brain that tracks what you fix your gaze on. Light can pass between the blades and form an image of the retina for at least some time. It's true that there are also blades blocking ...


2

Because human eyes and brains are slow, they cannot resolve the motion of the blades, but only see the average of the moving blades and the image in the background (this is actually primarily really due to the slow reaction time of the cones, which is slow, as is demonstrated by the fact that a 24 frames per second video does not appear as single images but ...


41

The eyes are measuring the number of photons of each color that are hitting a given point of the retina – that are coming from some direction. This is a function of time, $f(t)$, for each point. However, when this function is changing too quickly, the eye can't see the changes. Effectively, the eye may also see the average of $f(t)$ in each period of time ...


2

You've got your work cut out for you, so this answer can only point you in a direction. This calculation can be difficult because there is a profusion of pieces of terminology with subtly different meanings. Find a book/other source (but for the straight dope I suggest a book) which discusses radiometry and the differences between radiant flux, radiance, ...


5

An object at 1000K glows red because that is basically dominating the radiation that it is emitting that we can see. Most of the radiation it emits emerges in the infrared part of the spectrum to which our eyes are not sensitive. Your edited question asks about the appearance of hot metals. The chart below is an example of a "colour-temperature" chart for ...


0

This is a simple example of how red and blue light can mix so that they appear as green to the human eye. Let us take the example of two monochromatic time-harmonic light sources with frequencies $\omega_1$ and $\omega_2$. For simplicity let them both be cosines, then, \begin{align} f(t) &= A_1 \cos(\omega_1 t) + A_2 \cos(\omega_2 t) \\ &= 2 A_1 A_2 ...


4

Black is not a color, it is a shade. In physics, we call something "black" when it does not reflect any of the incident light. However, all black bodies radiate. The frequency of that radiation, the black body spectrum, is a function of the temperature of the object and follows Planck's Law: $$B(\lambda, T) = ...



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