= A compound microscope is made from an objective lens of focal length fo = 4 mm, and an eyepiece of fe 15 mm. The objective lens is moved close to the object so that an intermediate image is formed 20 cm above the objective lens, and the eyepiece is set at its own focal length above the intermediate image, forming a virtual image at infinity for the user's eye. If the object is 0.1 mm in diameter, calculate: i) the required distance of the objective lens above the object. ii) the diameter of the intermediate image. iii) the angular size of the image to the user's eye. iv) The system angular magnification, defined as the angular size in (iii) divided by the angle subtended by the object to the naked eye from a distance of 25 cm.