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Original poster

Help settle an argument between me and dh. Diagram attached

56 replies

CovidCorvid · 08/09/2021 19:02

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.

Help settle an argument between me and dh. Diagram attached
OP posts:
Thread gallery
6
hoola23 · 08/09/2021 19:06

@CovidCorvid physics is not my strongest subject but, I would say you are correct!

ApolloandDaphne · 08/09/2021 19:07

They can't see you if the Perspex is not slanted towards you in any way. Is it flat above them?

Original poster
CovidCorvid · 08/09/2021 19:09

[quote hoola23]@CovidCorvid physics is not my strongest subject but, I would say you are correct! [/quote]
Excellent.

To be honest physics isn’t my strong point and dh is an engineer so I’m slightly worried but reflections go at right angles pretty much? I can only see them because of the height of their Perspex ceiling. If they look up I reckon they can only see themselves.

OP posts:
Original poster
CovidCorvid · 08/09/2021 19:09

@ApolloandDaphne

They can't see you if the Perspex is not slanted towards you in any way. Is it flat above them?
Yes, it’s flat….maybe a slight angle away from their house for rainwater but not angled towards us.
OP posts:
TheCanyon · 08/09/2021 19:12

I reckon you're right. Btw, that diagram is so horrendous it is brilliant.

I guess it's a bit like my gloss kitchen cupboards, if I open them then I can see right along my neighbours gardens, but you can't see into that far back in my kitchen when you stand in their gardens. Bonus of you can't be eased chatting but need to go out back Grin

BrieAndChilli · 08/09/2021 19:12

Hold a mirror over your head- can you see something over the other side of the room?

Aquamarine1029 · 08/09/2021 19:13

They can NOT see you. Your husband is being ridiculous.

Realyorkshiretea · 08/09/2021 19:14

You’re correct. From someone who got a D in physics A level.

Original poster
CovidCorvid · 08/09/2021 19:15

@BrieAndChilli

Hold a mirror over your head- can you see something over the other side of the room?
We’ve already tried this. I got him sat in the bed holding a mirror above his head but the mirror isn’t very big and his arms aren’t long enough so we struggled to recreate it.

I could just see him. He reckons if his feet had eyes (wtf) his feet would have been able to see me so he still reckons he’s right!

OP posts:
Original poster
CovidCorvid · 08/09/2021 19:15

@TheCanyon

I reckon you're right. Btw, that diagram is so horrendous it is brilliant.

I guess it's a bit like my gloss kitchen cupboards, if I open them then I can see right along my neighbours gardens, but you can't see into that far back in my kitchen when you stand in their gardens. Bonus of you can't be eased chatting but need to go out back Grin

My art is probably worse than my physics. Grin
OP posts:
YesItsMeIDontCare · 08/09/2021 19:18

You need to go round and have a look!

It depends on the position I think. For example, if I look in my bedroom mirror I can see the garden, but if I stand in the corresponding spot in the garden and look up I can only see the reflection of the bedroom ceiling.

HeronLanyon · 08/09/2021 19:19

I’m going to experiment with a mirror. If you don’t hear back there may have been an incident.
My strong instinct is that what works one way works in reverse with a reflective surface. The further from their head the Perspex is the greater the angle of sight (which is why you can see them). If it were stay 100 metres overhead you would be able to see quite a bit it your neighbourhood and they you.

Original poster
CovidCorvid · 08/09/2021 19:20

I can’t ask the neighbours or go round….we don’t know them that well and I don’t want them to think I’m being arsey about their new bus shelter.

I don’t mind if they could see me as the bus shelter when finished will have a solid wooden side against the boundary wall so will stop me seeing them. So even if they can see me it will be temporary.

OP posts:
HeronLanyon · 08/09/2021 19:21

Op - why did you choose such a hot night to get us all struggling with mirrors held high ? Grin

ImperfectTents · 08/09/2021 19:21

If you can see them they can see you

Original poster
CovidCorvid · 08/09/2021 19:21

I need to attach a mirror to the bedroom ceiling but fear dh might get his hopes up!

OP posts:
mineofuselessinformation · 08/09/2021 19:24

As long as you have sufficient lighting on, your DH is right. If the angle of the roof reflects light from them to you (so you can see them, which you can), light can travel back to them, making you visible.

MangoBiscuit · 08/09/2021 19:24

If the light from them is hitting the roof, and reflecting back to you, then light from you can reflect of the roof, back to them. If the angles match for you to see them, it can go the other way.

However, it will depend on light levels. If it's brighter on their side, then they're unlikely to actually see you. Chances of you being lit well enough for them to see your reflection, over all the light outside, during the day, are pretty slim. If they sit there in the evening, and you have your lights on, they probably can.

ApolloandDaphne · 08/09/2021 19:24

I have been and constructed an experiment to determine who is correct.

Pic 1 is the neighbour's patio made out is books and there is a mirror balanced on top. Neighbour is the black lipstick and you are the pink and gold one in your garden.

Pic 2 is my phone slid in to replace the neighbour and a photo taken. You can see you quite clearly on your patio.

I therefore conclude that your DH is probably correct. It likely depends where they are and where you are on your patio but they can probably see you at some points.

Help settle an argument between me and dh. Diagram attached
Help settle an argument between me and dh. Diagram attached
Hiddenmnetter · 08/09/2021 19:25

He is right- the right angle thing is for total internal reflection, but a reflection works both ways. It may be that because your further back you have a wider view than them, but if they stand at the right point if you can see them, they can see you

Hiddenmnetter · 08/09/2021 19:25

Refraction* not total internal reflection

ElliePascoe · 08/09/2021 19:28

I agree with your DH - if you can see them, then they can see you in theory (depending on where their eyes are - that's what he meant by saying if his feet had eyes Grin). But that doesn't mean that they can actually see you in practice, as the roof may not be reflective enough to show things that are very far away. So you get all the benefits of spying on your neighbours with no real risk that they can spy on you back!

OldTinHat · 08/09/2021 19:28

I love this thread OP! I'll also say you are 100% correct, your DH is wrong and please can you post more diagrams just to be absolutely sure because your stick person is adorable!!

Original poster
CovidCorvid · 08/09/2021 19:29

@ApolloandDaphne

I have been and constructed an experiment to determine who is correct.

Pic 1 is the neighbour's patio made out is books and there is a mirror balanced on top. Neighbour is the black lipstick and you are the pink and gold one in your garden.

Pic 2 is my phone slid in to replace the neighbour and a photo taken. You can see you quite clearly on your patio.

I therefore conclude that your DH is probably correct. It likely depends where they are and where you are on your patio but they can probably see you at some points.

I love this even if I’m wrong!
OP posts:
OrangeTortoise · 08/09/2021 19:30

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?

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