A small bulb is placed at the bottom of a tank containing water to a depth of 1 m. Find the critical angle for water air interface and also calculate the diameter of the circular bright patch of light formed on the surface of water [Refractive index of water=1.33]
PR=1m
Let C be the critical angle
n2sinC=n1sin90
n2n1sin=1
1.33sinC=1
sinC=34
C=sin−134
=48o
radius = PQ
PQPR=tan∠PRQ=tanC
sinCcosC=sinC√1−sin2C
34√1−916=3√7
PQ=3√7PR=3√7m