Homework SourseGiven a block of glass that is semi circular a laser pointer
Given a block of glass that is semi circular, a laser pointer, a protractor/ruler, an index card, design your own expiriment to observe and measure total internal reflection:
Describe how you would shine the laser onto the glass block, what angles you would measure and how you would determine the critical angle from your measurements.
Solution
Start from snell\'s law....Ni X sin Ai = Nr x sin Ar
for total internal reflection in your case Nr =1 Ni = 1.52 , sin Ar =1 as limit for crtical angle.
so, 1.52 x sin Ai =1
so, sin Ai = 1/1.52 = 41.14 deg.
ie beam comes at 41.14 deg to normal in glass ( ie radius ), if coming out of curved side then at 48.86 deg to the curved edge surface/ tanget .
it is cumbersome to solve for min/max angle of incidence into the glass from air and you need proroctracter ruler to trace back the point of entrance into glass from any edge of the semicircular disc, so that the point of total internal reflection lies on the curved surface. always keep inj mind to bend the drawn rays as per ref. index at point of entrance.
