Three black bodies A, B and C in the form of cubes of sides in the ratio `3 : 4 : 5` are kept at the same high temperature. The ratio of the quantity of heat lost per second by A, B and C will be

Options

A. `27 : 64 : 125`
B. `5 : 4 : 3`
C. `9 : 16 : 25`
D. `25 : 16 : 9`

Answer

C

Explanation

Heat lost/sec `prop` Area or `QpropA`
(As all bodies are black and have the same temperature.)
The surface area of a cube = `6L^(2)`
`thereforeQ_(1):Q_(2):Q_(3)=6xx3^(2):6xx4^(2):6xx5^(2)=9:16:25`