(a) Show that if the object O rn Figure c is moved from focal point n toward the observer's eye, the image moves in from infinity and the angle θ (and thus the angular magnification mθ) increases.

(b) If you continue this process, where is the image when mθ as its maximum usable value? (You can then still increase mθ, but the image will no longer be clear.)

(c) Show that the maximum usable value of mθ is 1 + (25cm)/f.

(d) Show that in this situation the angular magnification is equal to the lateral magnification.