, . : - ( ), . ( ). - . (, , ), (, , ). , () .
, v.
n = / v (1.1)
.
= 3∙108 / - .
(.1). , . .
α = α′. (1.2)
.
, , , , .
(1.3)
n1 n2 - ; n21 - ; β - .
.
(1.3), , , (n1 n2 ) β α. ( n1 n2) β α (. 2), , (. 2, ), . β = 90 º.
, (α). , , , . .
. 1,5 d = 5 α = 30º . l .
. . 3. , β:
, β = 19º30′.
l ∆ BED:
l = BD∙cos α.
BD , ∆ BD:
BD = 2 = 2d tg β.
l = 2d∙tg β∙cos α =2d∙tg 19º30′ ∙cos 30º = 2∙5∙0, 3541∙0,8665 = 0,3063 ().