Light-Mirror Question?

Question

f is + if the mirror is a concave mirror
f is - if the mirror is a convex mirror

what dooes this mean?(lense-makers equation 1/f=1/distance of objct+1/distance of image)

ok, so does this mean that if im solving a problem for a concave mirror, and lets say the problem says the focal point is 15 cm away. Do i plug in -15 into the equation instead of 15? because of

f is "-" if the mirror is a convex mirror

Answer 1

In a convex mirror the image is behind the mirror, so when you measure the distances the signs to the object and to the image, one is plus and one is minus.