Ice starts forming in lake with water at `0^(@)C` and when the atmospheric temperature is `-10^(@)C`. If the time taken for `1 cm` of ice be `7` hours. Find the time taken for the thickness of ice to change from `1 cm` to `2 cm`

Options

A. 7 hours
B. 14 hours
C. lt 7 hours
D. gt 14 hours

Answer

D

Explanation

(4) `t prop (x_(2)^(2) - x_(1)^(2))`
`(7)/(t_(0)) = (l_(2) - 0)/(2^(2) - 1^(2)) = (1)/(3) implies t_(0) = 21 hr`