Calculating Object Distance from Lens with Magnification and Focal Length

[hardwork]

Homework Statement

An object is in front of a lens with a focal length of -15cm. An image ½ the side of the object is formed. How far is the object from the lens?

Homework Equations

m - magnification
q - distance from image
p - distance from object
f - focal length

m = -q/p
1/p + 1/q = 1/f

The Attempt at a Solution

m = -q/p so q = -(1/2)p

1/p + 1/q = 1/f
1/p + 1/(-1/2p) = 1/-15cm
-1/p = 1/-15cm
p = 15 cm

 

[rl.bhat]

Your answer is correct.

 

[hardwork]

woohoo!