1 g of ice take 334 J of energy to melt in to water = 4.0*10
2
Thus the amount of energy required to melt the 400 g of ice = 400 g * 334 J /1 g = 133600 J
The wave length corresponds to this enery = E = hc / λ
133600 J = 6.0*10-34 J.sec * 3.0*108 m/sec / λ
Thus wave length, λ = 1.34*10-30 m
Hence the number of photons that are absorbed at 660 nm = 1.34*10-30 m / 660*10-9 m
= 2.03*10-24 nm
b) 2.03*10-24 of photons converts the 400 g*6.023*1023 /18.0 g/mol of H2O molecules, hence -
1 photon converts the number of H2O molecules = 400 g*6.023*1023 /18.0 g/mol *2.03*10-24
= 6.593