Question

If work done by an agent to form a bubble of radius R is W , then how much energy is required to increase its radius to 2R...?

Answer 1

as per the question 
R1 = R, R2 = 2R
NOW THE INITIAL WORK DONE (W) IS = 8πR²s
and FINAL WORK DONE (W)= 8π[R2² - R1²]s
8π[4R² - R²]S
3 x 8πR²s  =  so W = 3W AS THE W IS EQUAL TO 8πR²S

Answer 2

NOW THE INITIAL WORK DONE (W) IS = 8πR²s
and FINAL WORK DONE (W)= 8π[R2² - R1²]s
8π[4R² - R²]S
3 x 8πR²s  =  so W = 3W AS THE W IS EQUAL TO 8πR²S