alleryGlass n=1.5, sin i=0.8. Outside is air n=1 or water n=4/3. TIR occurs with
ABoth media
BAir only
CNeither medium
DWater only
Answer & Solution
Correct answer: B. Air only
The critical sine is 2/3 for air and 8/9 for water, so sin i=0.8 exceeds only the air-boundary threshold.
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