Question

At X University, an optical system is used to monitor the movement of rats. The optical system consists of two biconvex lenses and a camera without a lens to observe the rats. The system has a lens (lens) with a focal length of 30 cm which is placed 40 cm from the mice and before the camera sits an eyepiece with a focal length of 20 cm. By varying the distance between the lens and the eyepiece, the focus position of the optical system can be changed. If the distance between these two lenses (lens and eyepiece) is varied between:

a) 1.5 m; b) 1.3 m; and c) 1.1 m, three configurations of the optical system are obtained. For each configuration (three pieces) specify: where the final image will end up, ie where the camera's detector should be placed; and what the total magnification will be. Are the images straight or inverted? Are they real or virtual?

d) What does an aperture stop have for function in an optical system? Give an example.

Answer 1

d)aperture stop also known as the f-stop regulates the amount of light that can pass through a lens at a given shutter speed. Assuming nothing else changes, a small aperture will let in less light than a larger one, so it would take longer for the same quantity of light to pass through to the sensor. It works on the same principle as an hourglass, in that the size of the opening between the two chambers dictates how long a quantity of sand will pass from the top to the bottom.

Example:Aperture stop is used in digital cameras