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Is it possible to directly see your own reflection in water?

by Curious1977
Tags: mirror, reflection, water
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Curious1977
#1
Aug7-11, 04:18 AM
P: 2
I've been curious about this question and hope that someone can provide a definitive answer with support for that answer.

Is it possible to directly see your own reflection in water?

From my understanding of reflections and my own observations I would say that it's not possible to directly see your own reflection in water. Below are details for why I think this. Please comment on why you think I'm right or why you think I'm wrong.

The strength of reflections varies based on the viewing angle. In computer graphics this is referred to as fresnel effect. Not sure if it's called something different in the physics community. The greater the angle of incidence the more reflective a surface will be. Very interesting effect. Often you'll see a surface that has only minimal reflectivity when viewed straight on but when you move to the side the reflection intensifies, sometimes even becoming mirror like. In order to see your reflection in something the angle of incidence can't be too great. Using a mirror as an example if you step to the side, increasing the angle of incidence, your reflection will move out of your own view. Of course with a mirror you can stand straight on and see your reflection, but water isn't as reflective as a mirror so the angle of incidence needs to be greater to see reflections. So it appears to me that with water you'd need to be at a viewing angle that's almost straight on to see your reflection but since the angle needs to be fairly great to see reflections in water these two things essentially make an impossible situation in which you can't see your reflection in water.

Hope that made sense. I should also say that my thoughts above are assuming that water isn't reflective at all at a straight on angle. It would guess that water is at least a bit reflective at a straight on angle but perhaps not reflective enough to notice your own reflection.

I'd love read peoples responses that explain in detail why or why not this is possible.

Thanks
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Redbelly98
#2
Aug7-11, 10:03 AM
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Welcome to Physics Forums. FYI, I have moved your post to "Classical Physics", since it's more of a classical physics question about light and reflection.

While the reflectivity when viewed straight-on is small, it is not zero. For water it's 2%. Enough light from you is reflected off the water surface, and back into to your eye to form the image that you can perceive. This is a direct observation of your reflection; have you never seen it yourself?

What might prevent you from seeing the image is if there are brightly lit objects under the water that overwhelm the brightness of your image. So looking at a white bathtub full of water might not show your reflection. But if you do this at night with the lights off, and a flashlight shining on your face, you should be able to see your image in the bathtub.
A.T.
#3
Aug7-11, 10:53 AM
P: 4,076
Quote Quote by Curious1977 View Post
Hope that made sense. I should also say that my thoughts above are assuming that water isn't reflective at all at a straight on angle. It would guess that water is at least a bit reflective at a straight on angle but perhaps not reflective enough to notice your own reflection.
Have you never looked down from a bridge when the sun already went down, but the sky was still quite bright? The water is dark, and you can see your dark contour.

I'm sure you can also create conditions where you can see your own face. Just keep the water dark, and the face well lit.

Curious1977
#4
Aug7-11, 01:42 PM
P: 2
Is it possible to directly see your own reflection in water?

That's great. Thanks for the replies. This questions has been on my mind for a while and I'm glad to have answers from people with a background in physics. I'm very curious about how things work. I just hope I didn't come across as totally ignorant.

Also I appreciate the examples listed in the replies. Quite helpful.

Thanks again.
chrisbaird
#5
Aug8-11, 02:28 PM
P: 617
Take a walk by a pond on a bright day and you will see that you can see your reflection just fine. A pond is a common poor man's mirror.
A.T.
#6
Aug8-11, 02:47 PM
P: 4,076
Quote Quote by Curious1977 View Post
I just hope I didn't come across as totally ignorant.
More like totally theoretical. You should go out more.
xts
#7
Aug8-11, 03:24 PM
P: 882
Oh, just leave behind all modern technology - like elecricity and tap water - and wash your face in a bowl of water while paraffin lamp stands on a table.


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