Q6. Hi please help with each question in photo. Will give thumbs up thanks!

For light of wavelength 589 nm, calculate the critical angles for the following substances when surrounded by air. fused quartz benzene crown glass A light ray travels through three parallel slabs having different indices of refraction as in the following figure. The rays shown are only the refracted rays. Rank the materials according to the size of their indices of refraction, from largest to smallest. nc On > na > nb Onb > nc > na Ona > nb ? no Ona > nc > nb