# Optics of Vehicle Convex Mirrors

I recently got in an argument with a friend while I was driving. When I moved to a different lane, I did not turn my head to check for any vehicles in my blind spot. Instead, how I checked was by leaning toward the rightmost region of the drivers wheel, looking into the left side mirror to see the field that is normally the blind spot when sitting upright. I've been doing this for several years, I imagine if I was wrong then surely I'd have gotten in an accident by now.

My friend, however, refuses to believe that works. He thinks the blind spot remains fixed no matter where the observer (driver) looks at the mirror or that at least it is not safe/effective as turning your head to look into your blind spot.

I understand mirrors in vehicles are convex mirrors, they slightly bulge out to increase the field of view for the observer (which is why objects appear closer in the mirror and why there is slight distortion). And I know as light hits the mirror, the mirror reflects it back outward. What I'm struggling with is how to explain that the position of the observer changes the blindspot.

How should I make my case?

• en.wikipedia.org/wiki/… Nov 8, 2021 at 22:46
• Can't tell if you're talking about the driver's side mirror (left-hand drive automobile) or the passenger's side (left side mirror, right-hand drive.) You said, "I understand mirrors in vehicles are convex mirrors." Here in the U.S.A., The driver's side mirror always is flat. Only the passenger-side mirror is curved. We presume that the driver's eye is close enough to the flat, driver-side mirror to provide a sufficient field of view. The passenger-side mirror, being much further from the driver's eye, would give only a very narrow view if it were not curved. Nov 9, 2021 at 1:33
• im talking about the drivers side mirror, the left side mirror Nov 9, 2021 at 1:34