Reckoning / Light / Free bench
Light · sandbox
Free bench
Add optical parts, drag them anywhere, turn them, and aim the light. Drag the yellow dot to move the source and the small ring to aim it. Tap a part to select it, then turn, resize, change its material or remove it. Everything is traced exactly, as on the other pages.
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The light
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Things to try
- Put two converging lenses in a row, a short focal length behind a longer one, about the sum of their focal lengths apart. That is a Keplerian telescope: a parallel beam goes in and a narrower parallel beam comes out.
- Send a single ray into a right-angled prism through its long face. It comes back out the way it came, totally reflected twice.
- Aim a narrow beam at a glass drop and at a water drop. Compare where the light that reflects once inside comes out.
- Put a diverging lens in a converging beam just before the focus. The focus moves back: that is a Barlow lens, or the back half of a telephoto lens.
- Tilt a block of glass in a beam. The rays come out parallel to how they went in, only shifted sideways.
These are rays, the geometrical-optics picture: light is treated as lines that bend and split at surfaces. Diffraction and interference, which need the wave picture, are not shown. The bench is a flat cross-section, so a lens here is really a cylinder of glass seen end-on. That is exact for rays in the plane of the drawing. Air is taken as n = 1, and the glass and water indices are given relative to air, so the angles are right. Colours on screen are an approximation of the spectrum.