What is black light and how does it work?

What is black light and how does it work?

Black light is ultraviolet light. You cannot see it so a room illuminated only by ultraviolet light appears dark or “black”. However any fluorescent materials in the room (e.g. brighteners in your clothes) will absorb the ultraviolet light and reemit it as visible light. That is why things with fluorescent pigments on them glow when illuminate by black light.

Why is it any worse to observe a solar eclipse rather than a normal glimpse at t…

Why is it any worse to observe a solar eclipse rather than a normal glimpse at the sun?

The problem with looking at the sun during a solar eclipse is not that it is somehow brighter than normal but rather that (1) you tend to stare at it and (2) the size of its bright region is reduced so that it doesn’t hurt as much to stare at it. It’s hard to stare at the full sun because it feels uncomfortable but looking at a tiny part of the sun may not feel bad enough to make you avert your eyes. Nonetheless, that tiny part of the sun can cook your retina and cause permanent damage.

Does red or blue light bend more in glass?

Does red or blue light bend more in glass?

Blue light almost always bends more than red light because blue light almost always travels more slowly through glass than does red light. This phenomenon is known as dispersion However, there are some glasses that exhibit anomalous dispersion, where red light travels faster and bends more than blue light. Anomalous dispersion only occurs when there is a resonant absorption of light in the glass, typically because of some impurity atoms or ions in the glass or because of some transition that occurs in the glass itself. While the resonance will only absorb light at one particular wavelength, it alters the propagation of light at nearby wavelengths. At wavelengths just shorter than the absorbed wavelength, light travels anomalously fast through the glass so that it bends less than light that is somewhat redder in color.

What is Brewster’s angle?

What is Brewster’s angle?

When light reflects from a horizontal surface at an angle, the reflected light tends to be polarized horizontally. At a specific angle, Brewster’s angle, the light is completely horizontally polarized because any vertically polarized light that hits the surface at this angle is allowed to enter the surface without reflection. Since reflections from horizontal surfaces are mostly horizontally polarized, glare is mostly horizontally polarized. Polarizing sunglasses deliberately block horizontally polarized light to reduce glare.

Why is it that after swimming in a heavily chlorinated pool, you can see the spe…

Why is it that after swimming in a heavily chlorinated pool, you can see the spectrum around lights?

Your eye works very hard to keep all of the different wavelengths of light together so that they can form sharp images on your retina without any color errors. If you look at a white light bulb, all of the different colors from that bulb must arrive together on your retina or else you will see colors where they shouldn’t be. Keeping these colors together is no small task and is one of the biggest problems encountered by lens makers for cameras and telescopes. The chlorine in a pool evidently upsets your eye’s ability to control these color errors. However, I’m not sure what goes wrong or why chlorine causes this problem.