State with reason, how the linear width of central maximum will be affected if (i) monochromatic yellow light is replaced with red light, and (ii) distance between the slit and the screen is increased.

For the single slit diffraction,
For maxima (central):
Angular width = θ
θ is very small
θ ≈ sin θ ≈ tan θ = y/D
y = Dθ
y = (Dλ)/a
So, Linear width of central maxima = 2y = 2Dλ/a
(i) As we know that wavelength (λ) of red light is more than yellow light.
λred > λyellow
So, βred > βyellow
So, linear width of central maximum will increase if monochromatic yellow light is replaced with red light
(ii) If distance between slit and screen (D) is increased then also the linear width of central maximum will increase.