Compute focal length, image distance, magnification, refraction and total internal reflection.
An optics calculator solves the thin lens equation, mirror equation, Snell's law of refraction, and angle calculations for total internal reflection. These cover the geometric optics problems found in introductory physics, photography (focal length, depth of field), and applied optics (microscopes, telescopes, eyeglasses).
Geometric optics treats light as straight-line rays — accurate when feature sizes are much larger than the wavelength of light. For diffraction, interference, and polarisation, you need wave optics.
\frac{1}{f} = \frac{1}{v} - \frac{1}{u} \;;\; n_1 \sin\theta_1 = n_2 \sin\theta_2
Inputs: 10 cm focal length converging lens, object at 30 cm
Light travels slower in denser media (c/n where n is refractive index). When a wavefront hits glass at an angle, the part entering first slows down while the part still in air continues at full speed — bending the wavefront direction. Refractive indices: air 1.0, water 1.33, glass 1.5, diamond 2.42 (which is why diamonds sparkle: extreme refraction creates rainbow dispersion).
A converging lens with the object placed inside its focal length produces a virtual, upright, enlarged image. The brain perceives the image as if it were on the far side of the lens. The angular magnification is approximately 25 cm (the closest the unaided eye can focus) divided by the focal length: a 5 cm focal length lens gives 5× magnification.
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