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phetsims / bending-light

"Bending Light" is an educational simulation in HTML5, by PhET Interactive Simulations.
http://phet.colorado.edu/en/simulation/bending-light
GNU General Public License v3.0
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Wrong equation for reflected intensity? #416

Closed oliver-phet closed 10 months ago

oliver-phet commented 11 months ago

A user wrote in suggesting the reflected intensity equation in the teacher tips is incorrect. I double checked the calculations and I agree.

image

Should be: $$R_{II} = \left({n_i\cos\theta_i-n_t\cos \theta_t} \over {n_i\cos\theta_i+n_t\cos\theta_t}\right)^2$$ This provides the same results that the sim provides.

arouinfar commented 10 months ago

The user is correct. We had the wrong equation in the Teacher Tips, and it's been that way since the Java version, unfortunately. I confirmed the correct equation with model.md, sanity-checked the values in the sim, and then updated the Teacher Tips. I've uploaded the new version to the website, closing.