Snell’s law
The second angle from two indices and an incidence angle.
Open a calculatorThin lens
The thin-lens equation: 1/f = 1/u + 1/v, real-is-positive. Fill exactly two. Magnification is −v/u. A negative f is a diverging lens. If the object sits at the focal point, the image is at infinity. Not a thick-lens or camera app.
Image distance
30
Focal length
10
Object distance
15
Magnification
-2
Image distance: 30
f = 10 and u = 15 give v = 30 and magnification −2. Same units on all three lengths. The Snell page is refraction at a surface, not a lens.
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An educational estimate. Not medical, tax or credit advice.