A surface of area `1 m^(2)` kept perpendicular to the sun rays absorbs 3 MJ solar energy in one hour.
(a) What is the amount of solar energy absorbed by a solar heater when a surface of area of `9 cm^(2)` is exposed perpendicular to the sun rays for 4 hours.
(b) What is amount of time taken by this heater to boil 12 kg of water at `40^(@)C` if its efficiency is 60% ? specific heat capacity of water =4200 J `kg^(-1) .^(@)C^(-1)`

Explanation

(i) `Q =msDeltat` (ii) 567 kJ