I1/I2= A1^2/A2^2
I1= Initial intensity
I2= New intensity
A1= Initial amplitude
A2 = New amplitude
I1/ 2I1 = (2.8)^2 / A2^2.. We have to find A2.. So solve this you'd get the answer.. I think its 3.959 ..
Thank you very much ! this was very helpful
I wanted to know whether this formula can be applied to ALL the intensity questions Thank you again!