Question

A points source of light is placed at the bottom of jar having a liquid of refractive index 5/3.An opaque disc of radius 1.0 cm is placed on the liquid surface with its centre vertically above the source. What is the maximum height of liquid for which the source is not visible from above

Answer 1

measuring angles from the normal
sinTheta=3/5
from Snells law.
then using proprotion
height/4=1cm/3
height= 1.333cm