We've all seen them outdoors. Often attached to night light lamp posts,
I'm talking about the convex security mirrors used to monitor parking
lots, businesses, etc. I recently learned that most are parabolic in >design. I was hoping someone here could explain what is parabolic, the >opposite, interior side of the mirror (in other words, the non-mirrored >side)?
Thank you.
On Tue, 31 Mar 2026 14:30:20 -0400, George Garth <none@nowhere.com>
wrote:
We've all seen them outdoors. Often attached to night light lamp posts,
I'm talking about the convex security mirrors used to monitor parking
lots, businesses, etc. I recently learned that most are parabolic in
design. I was hoping someone here could explain what is parabolic, the
opposite, interior side of the mirror (in other words, the non-mirrored
side)?
The surface is paraboloidal.
It doesn't matter what side you're talking about.
A paraboloid (the surface you get if you rotate a parabola) obviouslyThe purpose of a security/safety mirror is to reflect light towards the same observer from a wide angle. That is why its reflecting surface is the
has two sides, one concave and one convex. In the case of the mirror
you're talking about, the convex side is the reflective surface. In the
case of a telescope mirror, it would be the concave side. Just depends
on the intent.
We've all seen them outdoors. Often attached to night light lamp posts,
I'm talking about the convex security mirrors used to monitor parking
lots, businesses, etc. I recently learned that most are parabolic in design. I was hoping someone here could explain what is parabolic, the opposite, interior side of the mirror (in other words, the non-mirrored side)?
Chris L Peterson wrote:^^^^^^^
A paraboloid (the surface you get if you rotate a parabola) obviouslyThe purpose of a security/safety mirror is to reflect light towards the same observer from a wide angle. That is why its reflecting surface is the concave (outer) one.
has two sides, one concave and one convex. In the case of the mirror
you're talking about, the convex side is the reflective surface. In the
case of a telescope mirror, it would be the concave side. Just depends
on the intent.
The purpose of a telescope mirror is to collect as much light as possible^^^^^^
and focus it. That is why its reflecting surface is the convex (inner) one.
The advantage of such a convex mirror, why it is used, is that it reflects light towards the same observer from a wider angle than the observer's viewing angle. Horizontal cross-section (view from above/below):
incident ray
.
+ .
v
+ .
.
+
`
+ `<-- reflected ray
`
+- - -` observer
. ^
+ . |
^ reflected ray
+ . __
^ incident ray |PE
|
reflecting surface (x = -y^2/4)
(view with a fixed-width font)
I'm talking about the convex security mirrors used to monitor parking
lots, businesses, etc.ÿ I recently learned that most are parabolic in design.
| Sysop: | Jacob Catayoc |
|---|---|
| Location: | Pasay City, Metro Manila, Philippines |
| Users: | 5 |
| Nodes: | 4 (0 / 4) |
| Uptime: | 493850:11:22 |
| Calls: | 146 |
| Files: | 547 |
| D/L today: |
6 files (97K bytes) |
| Messages: | 76,927 |