What is the formula for predicting the critical angle (angle of incidence that provides an angle of refraction of 90-degrees)? General Knowledge refraction angle critical-angle incidence beam laser internal + – MathsGee asked Apr 14, 2021 55% Accept Rate Accepted 8191 answers out of 14789 questions MathsGee Platinum 113k points Share your questions and answers with your friends. Facebook Twitter LinkedIn Reddit Email Vk.com answer See all 0 reply

Best answer 1 votes 1 votes The critical angle = the inverse function of the sine (refraction index/incident index) The equation is: \[ \theta_{\text{crit}} = \sin^{-1}\left(\dfrac{n_r}{n_i}\right) \] where $\theta_{\text{crit}}$ = the critical angle $n_r$ = refraction index $n_i$ = incident index MathsGee answered Apr 14, 2021 MathsGee Platinum 113k points comment Share ask related question See all 0 reply Please log in or register to add a comment.