if you look at reflection of street light from across a boday of water , it appears long in one direction but

Question

but not the other. explain plz???

Answer 1

Visible light is emanating from the street light in all directions. Some of this visible light is hitting your eyes, travelling straight from the street light to your optic nerve. This is what your brain determines as "the street light."

In addition to this, any reflective surfaces within a straight line of sight of the street light, are reflecting this light as well. Depending on the surface itself, the light is either reflecting in many directions if it's rough (e.g. the road surface below the light, which is why you see a big lit up area under the light), or in a straight line if it's smooth (like a mirror). If the body of water were completely still and flat, you would see one more reflection of the street light in the water. However, water tends to have small waves due to wind or weather, creating one point of reflection on the curve of each wave (one point between you, the wave, and the street light where light with reflect prefectly).

So, between your eyes, and the street light, is this body of water with many, many reflective points. The only visible light that's reflecting off this each smooth surface and hitting your eyes, is the visible light that's in a straight line of sight between you and the light. So you're seeing hundreds, thousands, millions of reflections of the street light in a straight line between you and the street light. This is why it's elongated between you and the light, and not the other way.

Light is also hitting the water either side of this elongated reflection, but it's bouncing off into a direction your eyes can't caputre it, since you're in the one, fixed place. If you move 2 steps to the right or left, you'll cease to see the reflected light you were looking at, and see some new reflected light instead - also elongated.

I hope that makes as much sense as it does to me :)

Answer 2

for the same reason a mirror turn,s everything in reverse but not up&down.