If the speed of light were `2//3` of its present value, the energy released in a given atomic explosion will be decreased by a fraction.

Options

A. `2/3`
B. `4/9`
C. `5/9`
D. `sqrt(5/9)`

Answer

C

Explanation

`E = mc^2`
`therefore` If c becomes `2/3 c` ,
then E' = `m((2c)/(3))^2 = 4/9(mc^2) = 4/9 E`
`therefore " Decrease in " E (DeltaE) = E - E' = E - 4/9 E = 5/9 E`
Thus energy is decreased by a factor `5/9`