Prism Lab vs Extempore

Prism Lab is an optics bench in your pocket. Put a piece of glass on the graph paper, aim the laser at it, and watch the light bend, bounce and split, with every angle measured for you. It follows the experiments from a school ray box kit, so it works as a companion to the lab or on its own. THE BENCH • Nine pieces: a simple surface, 45-90-45 and 60-60-60 prisms, rectangle, square, semicircle, convex and concave lenses, and an optical fibre. • Drag the laser and where it aims. The angles of incidence, refraction and reflection update as you move. • Tap any angle and type the value you want. The laser swings there so you can see how it gets to it. • One, three or five parallel beams, to find the focus of a lens. MATERIALS • 119 materials for the piece and for what surrounds it: glasses, liquids, gems and gases, each with its refractive index. • The critical angle is worked out for every pair, and you can see total internal reflection happen. COLOUR • White light opens into a spectrum, because each colour bends by its own amount. • 77 materials use published dispersion data. For the rest the app tells you the spread is an estimate. • Red, yellow, green, blue and violet lasers, in the width you choose. LIGHTS OFF • Turn the lights off and the beams glow, as in a dark classroom. NO STRINGS • No account, no ads, and no data collected. • Everything is free. If you find it useful you can buy the developers a coffee. In English, Spanish and French, for iPhone and iPad.

Extempore allows foreign language instructors and students to exchange video and audio assignments without having to schedule 1:1 interviews or take class time. By enabling the Extempore Parameters, Instructors ensure that the assignments students submit is extemporaneous speech and not the reading of prepared script. You must have a current username and password to use Extempore: please contact your teacher to obtain a sign up link.