Un rayon lumineux se propage dans un milieu \(n_1\) d'indice de réfraction \(1,69\).
Il pénètre avec un angle d'incidence de \(77°\) dans un nouveau milieu \(n_2\), homogène
d'indice de réfraction \(1,86\).
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Quelle est la mesure de l'angle de réfraction \(\alpha\) ?
On donnera la réponse en degrés, avec 2 chiffres significatifs.