I imagine some of the light will illuminate dust, and some of it hits stars and galaxies, but where does the rest of it go? Will it light up the edge of the universe, or does it simply redshift out into oblivion? If I hitched a lift with one of these photons of light, where would I end up?

Imagine a straight horizontal plank of length 3x10^8m.

From one end of the plank, a beam of light is shone above the plank 9.81m directly/vertically above the plank and parallel to the length of the plank.

If gravity acts 9.81ms^-2 along the plank, will the beam of light touch the plank at the end?

From what i think i understand about the way the eye works, we have cells which can identify either red, blue or green light, which i guess corresponds to a certain wavelength (475nm, 510nm, 650nm), yet yellow light, for example, has a wavelength of 570nm. Is this picked up only partially by red and green receptors? If this is the case, technology using 3 colours of pixels in screens must be perfectly adapted to human eyes, yet a new type of television has been released with a yellow pixel as well. Would that offer any advantage to colour perception, or is it just smoke and mirrors?

If you have a current going through a fluorescent bulb tube and you smash it, for a split second there is a yellow flash as the gas escapes. What I'm wondering is what causes the yellow flash if the light coming out originally is a mix of colours that make white light?

If I make a box out of mirrors, then open the box in order to to let light in, then I close the box. Why does light not stay stored in the box?

A man looks at a small lit lightbulb, 5m away. He perceives it as being of a certain luminosity.

A woman looks at the same bulb from a different point 5m away. All things being equal, she will perceive it as having the same luminosity.

There are an infinite number of points from which the bulb could be observed. Does that mean the bulb actually has infinite luminosity?