Why Does Water Refract Light and Improve Visibility?

In summary, when diving without goggles, the water around the eyes causes refraction of light and makes the image appear blurry. This is because the eye needs to converge all the rays to a single point at the back of the eye to see a focused image. However, when using goggles, the air-to-eye interface is restored and the eye can once again converge the rays, making the image clearer. Without goggles, it may not be possible for the human eye to adjust its focal length enough to see clearly underwater.
  • #1
harimakenji
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Homework Statement


If you dive without goggles, you can't see very clearly. Why?


Homework Equations





The Attempt at a Solution


I guess the reason is water around the eyes refracts the ray so that the image produced in the eye is blur. Right?

But why when using goggle we can see clearer? There is also refraction occurs when light travels from water to the goggle, so why the image produced isn't blur?
 
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  • #2
You need to understand that in order to see a focused image, the eye must converge all the rays from the object to basically a single point at the back of the eye.
If the light rays diverge, or converge at a point slightly ahead or behind the back of the eye then the image will appear blurry.

So, by the design of our eyes there is only so much distance from the front to the back with which the eye has to focus the light rays, and our eyes have been adapted to do so at an interface of air->eye.

Technically, though, all the eye would have to do to see underwater without goggles is adjust the focal length of the eye enough, but depending on the curvature this required it may not be possible for the human eye to achieve.

Now, when you use goggles, you restore the air->eye interface, so even though the incoming rays may themselves still be refracted from the goggles, the eye is now capable of converging those rays to a single point at the back of the eye once again.
However, due to the water->goggle->air this refraction can cause other distortions like objects appearing slightly out of position, which depends largely on the angle you are looking, but even though those rays were bent the eye can still converge them because it has an air interface inside the goggles.

BTW: I think the inside of the eye has an index of refraction very close to water (I could be wrong) in that case when you don't have goggles on there would be almost no refraction so the light rays would not converge properly.
 
  • #3
Thanks a lot for the explanation buddy !
 

1. Why does water refract light?

Water refracts light because it has a different density than air. This density difference causes light to change speed and direction when it enters or exits the water, resulting in the bending of the light rays.

2. How does water improve visibility?

Water improves visibility by refracting and scattering light, making objects and details easier to see. This is because water molecules absorb and scatter light, reducing glare and increasing contrast.

3. Does the temperature of water affect its ability to refract light?

Yes, the temperature of water can affect its ability to refract light. When water is heated, its density decreases, causing light to bend less. This can result in reduced visibility in warmer water.

4. Why is water more effective at refracting light than air?

Water is more effective at refracting light than air because it has a higher refractive index. This means that light travels slower through water than it does through air, causing a greater change in direction when passing through the water.

5. Can other liquids refract light like water?

Yes, other liquids can also refract light like water. The amount of refraction depends on the density and refractive index of the liquid. For example, oils and alcohol have a lower refractive index than water, so they will cause less bending of light.

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