A slit of width d is illuminated by white light (which consists of all the wavelengths in the visible range).
(a) For what value of d will the first minimum for red light of wavelength `lambda = 6500Å` appear at `theta = 15^(@)` ?
(b) What is the wavelength `lambda` of the light whose first side diffraction maximum is at `15^(@)`, thus coinciding with the first minimum for the red light?
`[(a) 2.5 mu m, (b) 4300Å]`