Java Physics



Lenses closely above objects

  • Drag the lens to move; right-click inside the lens to see the object picture without magnification.
  • The lenses are not thin.
  • The image is calculated on the assumption that the observer is far away from the lens and the object picture is put under and close to the lens.
  • This applet is written in full accord with Snell's law of refraction. Therefore, the magnified/diminished images seen perfectly match with the real cases. Click here to see a comparsion.
  • If either the ratio h/D or the index of refraction (n) is too large, opague region(s) may appear at the edge of the lens.
Indeed, this phenomenon is very common.
L1 L2

For instance, stand a transparent semi-circular block upright with its flat surface facing upward. When viewed from the top, the two ends of the upper flat surface do not show any image of the bottom paper. This is a phenomenon of the total internal reflection. Practically, this can serve as an easy method of finding the index of refraction of the block or a liquid filled in a hemispherical transparent bowl.


Internal Links :

Easy Method of Finding the Index of Refraction. (Pdf)

Refraction through prism (Applet)

Lens effect due to ripples (Applet)

Run Applet Online

Download Executable Jar File




  • The author (Chiu-king Ng) has the copyright on all the simulations in this website.
  • Email, where AA is the prime number following 7.
  • Last Update:2017-6-5