Question

When an object is placed 30.0 cm in front of a concave mirror, a real image is formed 60.0 cm

from the mirror's surface. Find the focal length.
Answer=20.0cm

I need the steps I have a final exam and I’m confused can someone help and type it please ?

Answer 1

1 / f = 1 / o + 1 / i = (i + o) / o * 1

f = o * i / (o + i) = 60 * 30 / (60 + 30) = 1800 / 90 = 20 cm

Both the object and image are in positive space for a mirror