We have been that frequency (y) varies inversely with wavelength (x).
We know that two inversely proportional quantities are in form 
 , where a is inversely proportional to b and k is constant of variation.
, where a is inversely proportional to b and k is constant of variation.
Our required equation would be 
 .
.
To find frequency of blue light, we will substitute 
 and
 and 
 in our equation as:
 in our equation as:


Therefore, the frequency of blue light is 764.