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. Less than 7 hours
D. More than 7 hours

Answer

D

Explanation

Time (t) `=(rhoL)/(2K theta)(x_2^2-x_1^2)`
`implies t prop ([x_2^2-x_1^2])/([(x._2)^2-(x._1)^2]) implies (7)/(t.)=(1^2-0^2)/(2^2-1^2)`
`implies t.`=21 hours