With 1 graduated optical bench, 1 converging lens (with its support), 1 diverging lens of unknown focal length, 1 illuminated "arrow" serving as an object (with its support), 1 screen (with its support) and 1 diaphragm: Write a protocol that will allow you to determine the mystery focal length of your divergent lens. You will have to repeat your method in order to obtain at least 6 distinct series of measurements leading to the focal length. Be careful, think you need to get a real picture to be able to locate it and take measurements. Clues to follow: Start by thinking about the signs of the 3 variables p, q and f of your divergent lens. 2 of the 3 signs are known, which ones and why? Next, write the thin lens equation and use it to determine the sign of the third variable. What does the sign mean? build your protocol accordingly.

With 1 graduated optical bench, 1 converging lens (with its support), 1 diverging lens of unknown focal length, 1 illuminated "arrow" serving as an object (with its support), 1 screen (with its support) and 1 diaphragm: Write a protocol that will allow you to determine the mystery focal length of your divergent lens. You will have to repeat your method in order to obtain at least 6 distinct series of measurements leading to the focal length. Be careful, think you need to get a real picture to be able to locate it and take measurements. Clues to follow: Start by thinking about the signs of the 3 variables p, q and f of your divergent lens. 2 of the 3 signs are known, which ones and why? Next, write the thin lens equation and use it to determine the sign of the third variable. What does the sign mean? build your protocol accordingly.