Is the Image from a 12cm Focal Length Lens Virtual or Real?

[mike2007]

A positive lens has a focal length of 12cm. An object is located a distance of 3 cm from the lens.
How far is the lens from the image?
Is the image real or virtual, erect or inverted?

My attempt
f = +12cm
o = +3cm
i =?
1/o + 1/I = 1/f
1/i = 1/f – 1/o
= 1/12cm – 1/3cm
= 1/12 – 4/12
= - (3/12)
i = -4cm on the same side of the object.

Since the object lies in within the focal point, the image is virtual and erect.

 

[mgb_phys]

Always draw the ray diagram before trying to do the maths.

 

[Kurdt]

Looks good to me.