The question is regarding Young's double slit experiment.
"Describe the effect, if any, on the separation and on the maximum brightness of the fringes when the following changes are made.
2) The wavelength λ is increased to 1.5λ, keeping a and D constant.
The Attempt at a Solution
Separation: Increases by 1.5 times
Maximum brightness: Same (Wrong, answer: less bright)
Why would the change in wavelength alter the brightness of the fringes?