Optical Board - Circular Slab
To show focusing of a circular lens.
Optical board with circular disc, concave and convex lenses to produce parallel rays.
Parallel rays incident on a 12 inch diameter circular plastic disc converge at the focal point. Spherical aberration is clearly seen. Number of slits and their spacing can be changed by choice of slit baffle and distance of baffle from source. This cylinder can also be used to produce a nice rainbow; see Demonstration N1-44: RAINBOW - OPTICAL BOARD.