Bukhovtsev-et-al-Problems-in-Elementary-Physics

392 ANSWERS AND SOLUTIONS
a
Fig. 506
Using the law of refraction, we can find the ratio ~~.
Indeed,
s~n i =n and sin (i +ai) =n
sin, sin (, +ar)
Remembering that ~i and ~r are small, we have
sin ~i ~ 8i, sin~, === ~" and cos L\i === cos ~, =:: t
Therefore, the last equation can be rewritten as
sin i+ cos i· Ai=n sin ,+n cos r-br
Ai cos r
Hence, T= n--., Uoon inserting this expression into the formula relating
cos l
a'