Why is it that when you fill up a tub with water it appears to be blue, but fill a glass and it is clear???

Question

Just can't figure it out, water in the ocean appears blue from reflecting the sky. But when there is no blue in the bath it still appears that way???

Answer 1

Interesting! I presume that you don't have blue walls or ceiling.
The only other option is that there is a small filtering effect of the tap water that is biased towards blue.

A glass of water is only 2 or 3 inches thick and you are seeing light that passed thru the water only once.

However, in the tub the water is 12 to 24 inches thick. Assuming that you have a white tub, you are seeing light that passed thru the water twice. Once from the light bulb to the tub surface, and once reflecting from the tub surface to your eye. So you are getting about 20 times the filtering effect that you would see in a glass of water. You could try looking a 1 or 2 inches of water in the tub to check this out.

Finally, the light bulb might matter. Some older fluorescent bulbs have a blue/green tint.

Answer 2

Because water is only very slightly blue (due to Rayleigh scattering, the same effect that makes the sky blue; there is no sky reflection going on) the amount of water in a glass looks colourless. When you have a lot of water, like a swimming pool, the light is traveling through many feet of water and appears distinctly blue.

Viewed from underwater, the light sources appear slightly yellower because they have had some of their blue light scattered away.

Answer 3

Water is a clear compound with NO color characteristics. Sure the water looks blue on a clear day, but go to the beach when it is raining out and you will see that it actually looks grey. The water is simply reflecting the dominant color around it which is blue. Some times the water may look green. This is due to plants animals or contamination within the water. On it’s own, water has no color.

Answer 4

Sure did not look blue to me...

Maybe your water has a few particles that are blue,. In the glass, nothing will help reflect the light around, so it's clear. In the tub, the particles get a little help from the tub itself, so it looks bluish.

Answer 5

Is your bath tub blue? The water in bath tubs always looks clear to me unless the tub is blue. Perhaps the wall and/or ceiling in your bathroom is blue? Those are the only reasons I can think of.

Answer 6

There is no way for blue color to reflect to it, because it can't hold the bluish light.

Answer 7

Is the bathtub blue? (P.S. to the moron above, water doesn't contain pigment)

Answer 8

Scattering of light(tubelight)

Answer 9

because there is not enough pigment in the water for you to notice the color in the cup.