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

Explanation

For first maximum `sintheta_1=(3lamda)/(2a)`
`thereforea=(3 lamda)/(2 sintheta)=(3 times650times10^-9)/(2 times0.5)=1.95 times10^-6 m`