View through a lens
University of Louisville Physics and Astronomy Module Project
John Kielkopf
MIT License Copyright (c) 2017 J. Kielkopf


Click Camera to enable controls for your point of view, or to reset to the default.

When controls are enabled, the mouse will move your point of view. Try different mouse buttons, the mouse wheel, and combinations of the shift and control keys with mouse click and drag to change the direction and your position in space.


D_1 in mm is the distance from the lens to the object.
D_2 in mm is your distance from the lens.
Click and drag on the bars to change these distances.

Lens Properties

Change the radius of curvature of the plano-convex lens or its index of refraction.
The new focal length will update automatically.


Click Reset to try again.



The focal length of a plano-convex lens of radius of curvature R is f=R/(n-1) where n is the index of refraction.

An object at infinity will be focused by the lens on a screen a distance f behind the lens, and looking through the lens your eye would have to focus on that virtual screen closer to you than the lens, to see clear image. It would appear inverted.

When the lens is placed closer to the screen than f, the image it forms is apparently behind the screen and farther from you than the lens. For use as magnifier it is conventional to adjust its distance such that the virtual image it makes is about 25 cm away, meaning that you would focus on that region to see a clear magnified image of the object.