Convex lens – object between lens and F

An object between the lens and F is an object placed between one principal focal length and the convex lens itself.

As always, we use the two important rules of ray diagrams:

1. From the object, pass a parallel line through the principal focal point.
2. From the object, pass a ray line through the centre of the convex lens.

We can see from the above diagrams that all the images are located on the same side as the object. An eye from the other side of the convex lens would not see the object but an imaginary one and bigger. This is what they call a magnifying glass. The image (if the object is located between the lens and one focal length) will always be bigger than the object, behind the object and upright (sometimes called erect). This image can only be observed in the above eye positions, the image can not be captured on a screen.

In summary this would be:

Or to make it really simple:

Or as a block diagram: