2007-08-25 00:47:50 · 6 answers · asked by April 5 in Science & Mathematics ➔ Physics
A number of misconceptions by other answerers.
The short answer is pretty much the opposite of what most people have said: Glass disappears in water because it refracts light the SAME amount as water (not differently from water, as most people have said). That is, glass & water have very similar optical densities (although that of glass is a little higher).
Light refracts (changes direction) when it travels from a medium of one optical density into a medium of a DIFFERENT optical density. The greater the difference, the greater the refraction. This refraction is exactly what allows us to "see" things that are transparent. The reason we can tell there's water in a cup, is that the light changes direction when it goes from the air to the water and again when it goes from the water to the air; so we see the distorted image characteristic of a cup full of water.
The optical density (a.k.a. "index of refraction") of air is about 1.0
Index of refraction of glass: about 1.4 to 1.5.
So, when you set a piece of glass on a table, the light reflects and refracts as it passes in & out of the air and the glass, due to the great difference between their indices of refraction. This lets you "see" the glass.
Index of refraction of water: 1.33
When you drop the piece of glass into water, the light passing from the water to the glass (& vice versa) does not reflect or refract very much--that is, it keeps going in the same direction--due to the fact that the indices of refraction of water & glass are similar (much more similar than AIR & glass). Since the light does not bend much, it "looks" the same as if there were no glass in there at all; i.e. the glass is invisible.
2007-08-25 03:25:01 · answer #1 · answered by RickB 7 · 2⤊ 0⤋
How come both of the above answers are exactly the same?
Anyway, I think that it is because the water refracts light quite a bit and glass (good glass at least) does not. You can see the refraction of water by sticking a pole or stick into some water, it looks like it is bending.
But when you look into the water you brain is already used to compensating for this effect, so the slight extra refraction or distortion from the glass just doesn't register with your brain.
Good Question
2007-08-25 01:14:40 · answer #2 · answered by Mugwump 7 · 1⤊ 0⤋
Glass is transparent like water so we deem it invisible.
Glass has a different optical density than water so if you turned it a certain way in water you would see a displacement of the glass due to the action of refractive index.
2007-08-25 00:55:05 · answer #3 · answered by Billy Butthead 7 · 1⤊ 0⤋
Glass is transparent like water so we deem it invisible.
Glass has a different optical density than water so if you turned it a certain way in water you would see a displacement of the glass due to the action of refractive index.
2007-08-25 00:58:40 · answer #4 · answered by bala 2 · 1⤊ 0⤋
The refraction of light can not happen here.The laws of refraction obey with diffrent media.There is no refraction or it is n=1.glass to water,water to water,,
and glass to glass .
2007-08-25 03:00:48 · answer #5 · answered by Tuncay U 6 · 1⤊ 0⤋
Rick B IS correct.
As for the top two "matched-pair" of answerers:
I know all about "Duplicate Identities" (Use them Myself), BUT... This is the first time that I've seen "Xerox Answers".
Are you two some species of CLONE, or what???
2007-08-25 06:02:06 · answer #6 · answered by Anonymous · 1⤊ 0⤋