Question

The number of quanta of radiations of frequency $4.67\times {10}^{13}{s}^{-1}$ that must be absorbed in order to melt 5 g of ice, if the energy required to melt 1 g of ice is 333 J, is:

• A. $5.38\times {10}^{22}$
• B. $53.8\times {10}^{22}$
• C. $5.38\times {10}^{24}$
• D. $0.538\times {10}^{22}$

Answer 1

The correct option is A $5.38\times {10}^{22}$

Energy required to melt 5 g of ice
$=5\times 333=1665J$
Energy associated with one quantum E
$=h\nu$ where $\nu$ is the frequency of radiation.
E $=(6.62\times {10}^{-34})\times (4.67\times {10}^{13})$
$=30.91\times {10}^{-21}J$
Number of quanta required to melt 5 g of ice
$=\frac{1665}{30.91\times {10}^{-21}}=5.38\times {10}^{22}$