Hi there, I am in need of another's thoughts on this topic. I at first thought frequency is something that doesn't change and is inherent to the source, so then increasing the wavelength shouldn't lead to an increase in frequency, but an increase in speed. I realized later that this only applied to situations where there is a change in medium, since speed is a property of the medium. I concluded that in situations with change in medium and constant source, the frequency will stay constant and the relationship holds for velocity/wavelength (directly proportional) = constant. However, if you were to change the source's frequency (a laser for example), in the same medium, the velocity is now constant and the relationship holds for f*wavelength (f and wavelength being inversely proportional) = constant. Please let me know if my way of thoughts are correct. Thanks.