A microwave oven operates at `2.5` GHz. Assume that `5%` of microwave photons are absorbed by 200 ml of water kept inside the oven. The time needed to warm the water from `20^(@)C `to `70^(@)C` is 2 minute. Specific heat capacity of water is `4.2 Jg^(–1) .^(@)C^(–1)`. Neglect any heat loss by water to the surrounding. Calculate the number of photons emitted per second per kilowatt of power consumed by the microwave. Efficiency of the oven to convent electrical energy into microwave energy is `70%`

Answer

`4.22 xx 10^(26)`