Answer
a) the thickness of the film should be increased if the green light is used.
b) $t_G=105nm$
Work Step by Step
(a) We know that the wavelength of green light is greater than the wavelength of violet light; hence the thickness of film for green light should be greater than for violet light and we conclude that the thickness of the film should be increased, if the green light is used.
(b) We know that
$t_G=\frac{\lambda_G}{4n}$
We plug in the known values to obtain:
$t_G=\frac{560\times 10^{-9}m}{4(1.33)}$
$t_G=105nm$
