Question

Below is one final diagram, this time with the object at the focal Point. Draw the ray diagram for this case. Note: you will only be able two of the three principal rays. Does it appear that the rays that have passed through the lens diverge from some point? If so, where? If not, why not? Predict what you will se when look back thru lens towards the object? While your head is far from the lens, look back thru the lens toward the object. While you continue to look, your partner should slowly move the object from a location where 0>F to a location where 0<F. What did you see when the object was located at the focal point of the lens?

Answer 1

One principle ray will pass through midpoint of lens and continues while other which is parallel to principle axis pass through focus and thus is parallel to other principle ray after refraction.

3.18) The rays don't actually diverge when the object is placed at focus, but they are parallel and can be assumed to meet at infinity.

3.4) The image is hghly enlarged and is at infinity. So we will not be able to see any image.

3.19) We will see a line made from object.