A layer of ice has formed on a very deep lake. The temperature of water, as well as that of ice at the ice-water interface, are 0° C, whereas the temperature of the air above is -10° C. The thickness L(t) of the ice increases with time t. Assuming that all physical properties of air and ice are independent of temperature, L(t)~L0tα for large t. The value of α is
1
1/4
2
1/3
3
1/2
4
1