Question

If two waves of intensities i and 4i superpose then the maximum and minimum intensities are

Answer 1

hope this helps I have provided the equation solve it for yourself

Answer 2

When two waves of 4I and I intensities superimpose each other
the resultant intensities of resultant wave can be be find by using the
formula
I = I 1 + I 2 + 2√I 1√ I 2 cos©
In case of finding max intensity in place of cos © you have to put +1.
Thus calculating the answer is 9I.
In case of finding minimum intensity you have to put -1 in place of cos © .
Thus by calculating we find the answer is I .