Help settle an argument between me and dh. Diagram attached

[CovidCorvid]

This is an urgent matter of physics -who is correct?

We live in a semi detached house. Next door have a rear extension so their house sticks out further. Right outside their patio doors they’ve built a patio which they have covered over with a Perspex roof (no sides).

When I’m sat at the dining room table looking out of my patio doors I’m obviously lower than their Perspex roof which is extremely reflective. So if they are on their patio I can see them in their roof/ceiling as I can see the underneath of the Perspex from my angle.

Dh reckons if I can see them then they can see me. I don’t think they can because the Perspex roof is not pointing at me, it’s pointing down at their patio.

@OrangeTortoise

They can only see you if they sit staring upwards at the ceiling though, right? (Unless I have misunderstood the helpful diagram.) So effectively they can't?

Yes, but even then I didn’t think they could see me if they were looking up. I just thought they’d see themselves.

Wave at them and see if they wave back

He's right.

Light will reflect off the roof at the same angle it hits it. Like when you play pool and the ball bounces off the cushion.

But, if they're in bright light then there's lots of light being reflected towards you. If you're in dimmer light then there's less 'you' light bouncing towards them. If you're looking through a window then there's also the liklihood that sunlight will be bouncing off your window towards them and sort of diluting the 'you' light.

If they sit under their shiny roof in the dark, and you have your room light on, they'll probably be able to see you really clearly.

A swimming pool with a glass roof near me had to put an extra roof on all the changing cubicles because if you looked up in the ladies section you could see right into the men's cubicles, and vice versa.

I got as far as "if his feet had eyes" and lost track of the whole point.

Diagrams to explain better. Maybe.

I've taken a photo from my back door. They're not outside at the moment so not in the photo. Really hope they're not on MN! 🤣

It's effectively a mirror and if you can look someone in the eye in a mirror, they can see you.

@Astraturf

Wave at them and see if they wave back

🤣🤣🤣🤣 love it!

Of course they can see you. Haven’t you ever tried looking ‘into’ a mirror? You can see things that aren’t directly in front of the mirror because it’s to do with the angle you’re looking from. That’s what your Dh means when he’s talking about eyes on his feet.

Can’t you take round some food?

Your neighbour looks awfully thin.

Mango has it right, so does your DH.

When you see your neighbours, can you see their eyes, feet or the tops of their heads?

@MangoBiscuit

Diagrams to explain better. Maybe.

I have been hoping someone would do this diagram so I didn't have to 😅 spot on! They can see you but you have to be in the right place (ie the place where you are when you can see them).

Also light doesn't reflect at a right angle. When light hits a flat reflective surface it will be reflected at the same angle as it hit but on the opposite side. Here's a picture:

@Postdatedpandemic

Mango has it right, so does your DH.

When you see your neighbours, can you see their eyes, feet or the tops of their heads?

I'm trying not to look that closely. It's more movement I see out of the corner of my eye, then I look up and realise I can see them and look away. Mainly tops of heads I think though I guess if they were sat down I'd see their legs.

@Astraturf

Wave at them and see if they wave back

This! Def this!!

It stands to reason that if you could see their eyes from where you are, they could look up and see your eyes. And thus you’d be looking at each other.

I agree they’d probably not be looking up a lot though so unlikely it’s going to cause a problem. For you. For them it might be easy fit you to spy on them all night.

I won’t be spying on them at all! Only time I’m in the back room is if I’m working and I have my head down in the laptop then 99.9% of the time.

Ask them.

What if they want to, um, shag get intimate out there? 😂😂

@CovidCorvid 'Only time I’m in the back room is if I’m working and I have my head down in the laptop then 99.9% of the time.'
So you're ok as long as you're not working with your foof and norks on show then! (That could be a bit awkward when getting to know them....)

If you can see them then they can see you, if they choose to look up at their ceiling

Just don’t look at the ceiling 😎😎😎

it's probably like the shiny surfaces on the tube where you get startled and watch away in shame when you meet the eye of another person.

so yes, they could see you but probably haven't noticed that they could yet

Your neighbours will not be able to see you as the angle of the perspex, if it was angled the other way towards your house then they would be able to see you, but as it is angled down away from you they will not be able to see you and as the light reflected on the perspex it bounces off to give a mirrored look an the angle of the a mirror pointing down like that will not catch you in the reflection.

I love the idea that a reflective surface just reflects the people underneath it no matter where/who is looking at it . Like a photo.

I totally agree the way mirrors work doesn’t seem to make sense but you know it does work like that.

@Jux

What if they want to, um, shag get intimate out there? 😂😂

I’m hoping they put the side wall on first and then I won’t be able to see! 😂😂🙈