A Slit of width a is illuminated by monochromatic light of wavelength 650nm at normal incidence. Calculate the value of a when
the first minimum falls at an angle of diffraction of `30^@`

Explanation

for first minimum `sintheta_1=lamda/a`
`thereforea=lamda/(sintheta_1)=(650 times10^-9)/(sin30^@)=1.3 times10^-6m`