When a fish looks up the surface of a perfectly smooth lake, the surface appears dark except inside a circular area directly above it. Calculate the angle that this illuminated region subtends. Given `mu` of water `= 1.333`.

A salt water lake has refractive index 1.4. A fish when looks towards the surface of water, can only view things outside through a circular area. Calculate the semi-vertical angle of the cone formed within which the circular area lies.

A ball is dropped from a height of 20m above the surface of water in a lake. The refractive index of water is 4//3 . A fish inside the lake , in the line fall of the ball, is looking at the ball. At an instant when the balll is 12.8m above the water surface, the fish sees the speed of ball as .

A point source is placed at a depth h below the surface of water (refractive index = mu). (a) Show that light escapes through a circular area on the water surface with its centre directly above the point source. (b) Find the angle subtended by a radius of the area on the source.

A point source is placed at a depth h below the surface of water (refractive index = mu). (a) Show that light escapes through a circular area on the water surface with its centre directly above the point source. (b) Find the angle subtended by a radius of the area on the source.

A point source is placed at a depth h below the surface of water (refractive index = mu). (a) Show that light escapes through a circular area on the water surface with its centre directly above the point source. (b) Find the angle subtended by a radius of the area on the source.

In a river 2m deep a water level measuring post embedded into the river stand vertically with 1 m of if above the water surface.If the angle of inclination of sum above the horizon is 30^(@) , calculate the length of the post on the bottom surface of river , ( mu for water = 4/3 ) 3.44 m

A bird in air looks at a fish vertically below it and inside water. h_(1) is the height of the bird above the surface of water and h_(2) , the depth of the fish below the surface of water. If refractive index of water with respect to air be mu , then the distance of the fish as observed by the bird is

A point source of light is placed directly below the surface of a lake at a distance h from the surface. Find the area surface of a lake at a distance h from the surface. Find the area on water from which the light will come out from water. [(pih^(2))/((mu^(2)-1))]