A. a beam of light is incident from air on the surface of a liquid. if the angle of incidence is 26.7° and the angle of refraction is 18.3°, find the critical angle for the liquid when surrounded by air? b. a light ray, traveling in air, strikes the surface of abeaker of mineral oil at an angle of 37.5° with thenormal to the surface. the speed of light in mineral oil is 2.17 x10^8 m/s.. calculate the angle of refraction.

Lake happy times contains 100 km3 of pure water. it is fed by a river at a rate of 50 km3/yr. at time zero, there is a factory on one shore of lake happy times that begins introducing a pollutant to the lake at a rate of 2km3/yr. there is another river that is fed by lake happy times at a rate that keeps the volume of lake happy times constant. this means that the rate of flow from lake happy times into the outlet river is 52km3/yr. in turn, the flow from this outlet river goes into another lake, lake sad times, at an equal rate. finally, there is an outlet river from lake sad times flowing at a rate that keeps the volume of lake sad times at a constant 100 km3 . (a) find the amount of pollutant in lake sad times at the end of 3 months. (b) at the end of 3 months, observers close the factory due to environmental concerns and no further pollu- tant enters lake happy times. how long will it take for the pollutant in lake sad times (found in part (a)) to be cut in half?