image distance physics question , please help :)

Question

A diverging lens with f=−42 cm is placed 33 cm from a jar of marshmellow fluff. Find the image distance. meters. to a precision of tenths of a cm.

Answer 1

Use the formula

 

1/p + 1/q = 1/f

 

p = object distance = 33 cm

q = image distance = ?

 

Remember the focal length of a diverging lens is negative.

 

1/q = 1/f - 1/p

 

q = 1 / (1/f - 1/p) = 1 / (-1/42 - 1/33) cm = -18.5 cm

 

The negative sign means the image is on the same side of the lens as the object.