How can a window screen be see-through from one side, but barely the other?

Question

I have a window in my current living space that’s a simple, single-hung window, and on the outside is fitted with a fine mesh window screen to minimize bugs coming in. Inside, I have a perfectly clear view of the outdoors – I can see the front yard, the road, my neighbor’s house, with no significant or even noticeable obstruction from the screen. Yet, on the outside, you can barely see in through the window at all – even with sunlight streaming in and illuminating the room, you can only see basically what’s right against the window, nothing beyond that. Though I’m sure this is a fully intentional privacy feature, I’m terribly curious about how that can be, that one way the screen provides next to no obstruction, yet the other it’s almost completely obstructing the view. From what I understand about vision, we see based off light particles bouncing off the subject into our eyes, so… is the outside of the screen somehow absorbing light particles? It isn’t even especially dark, just a sort of medium grey fine metal mesh…

Thanks in advance!

In: 5

Answer 1

Imagine you have a screen that reflects 50% of the light and allows 50% through. Outside you have 100 units of light and inside you have 10 units of light.

If you look at the screen from the outside you get 5 units of light from inside, and 50 units of light reflected back from outside. What you see is 90% outside light so it is hard to see what is inside.

If you look at the screen from the inside you get 50 units of light from outside, and 5 units of light reflected back from inside. What you see is still 90% light from outside so it is easy to see what is outside.

The key is the significant difference between the amounts of light in each area. This is the basic idea behind how “one-way mirrors” work, they are just partially reflective mirrors and the observation room is very dark compared to the interrogation room.