Which equation states the law of refraction for a ray crossing from medium 1 into medium 2?

1. The law of refraction, also called Snell's law, is written n1 sin theta1 = n2 sin theta2. 2. Here n1 and n2 are the indices of refraction of the two media. 3. The angles theta1 and theta2 are measured between the rays and the perpendicular in medium 1 and medium 2. 4. Pairing each index with the angle in the other medium, as the last option does, reverses the bending and gives the wrong answer. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.3 The Law of Refraction_