Why is water deeper than it looks

The light travels in such a way that the pool often appears to be shallower than it really is. A normal is a dotted line drawn perpendicular to the surface of the refracting material, at the point of entry of the light. When light travels from air into a denser medium like water or glass, it will refract towards the normal. Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue.

See Subscription Options. Discover World-Changing Science. He sent the following reaction: "The answer to why the sky is blue isn't quite correct.

Get smart. Sign up for our email newsletter. But why does the ocean appear to be dark blue in some places, turquoise in others, and sometimes yuck more of a brown color? Before researching this topic, I thought it was simply a matter of how deep the water was where I was looking: the darker the blue, the deeper the water. It turns out that I wasn't completely wrong, but there's a lot more to it than that. In very deep water, almost all of the sun's rays are absorbed by the water itself due to the lack of sediment and the lower amount of organic matter like algae and jellyfish , and thus the blue appears to be darker.

In shallow water, on the other hand, floating particles like sand, silt, algae, and corals absorb light wavelengths differently than water, which can change the color of the water we see. For example, in regions with high concentrations of phytoplankton which have chlorophyll that absorbs red and blue light and reflects green , the ocean will appear in shades ranging from blue-green to green, depending on the type and density of the phytoplankton population there.

Basically, says NASA , "the more phytoplankton in the water, the greener it is And how about water that appears to be varying shades of brown? The best freestyle swimmers win races by operating with straight arms and long pulls. The intended effect of the arms is to pull water backwards and by maneuvering with longer arms as opposed to swimming with bent elbows, more water is able to be pulled towards the swimmer and then pushed backwards. Stretching those arms forward first brings the swimmer closer to their finish line and by pulling their arms back down to their thighs not just to the stomach or hip , more water is then pushed backwards behind the swimmer , leaving less water in front of the swimmer to resist.

So sure, the non-swimmer is correct to say that swimmers move their arms and feet but it cannot stop there. We must acknowledge the immense effort of the aquatic athletes to control their body movement, to strategically place various body parts, such as the chin and the arms, while still appearing to swim seamlessly through the water.