A lake has a surface area of 410 m2 and a volume of 1140 m3 . Suppose that during the day, sunlight with a power averaging 820 W/m2 shines on the lake, and that about 10% of this power is absorbed in the lake, producing heat. Assume that the temperature of the lake water stays constant because the absorbed solar power is exactly balanced by heat lost due to evaporation of water from the lake surface. What is the evaporation rate, in g/s

Explanation:

Total solar energy falling on total surface per second

= 410 x  820 W

= 336200 W

10 % of 336200 = 33620 J is converted into heat which is absorbed by lake water . But its temperature does not rise because heat is used up in evaporating water in the form of vapor .

Total heat released during evaporation = 33620 J

Let evaporation rate be m gram /s

heat absorbed by m gram water = m x latent heat of evaporation

= m x 2260 J .

Given ,

m x 2260 = 33620

m = 14.87 g /s .