Answer:
0.776 m far Pinhole should be placed before the viewing screen
Explanation:
For circular aperture of diameter D will have a bright central maximum of diameter, width is given by
[tex]w=\frac{2.44 \lambda L}{D}[/tex]
where [tex]\lambda[/tex] is wavelength of helium neon laser = 633 nm, D=10.cm, w=0.12 mm
Pinhole should be placed before the viewing screen is
[tex]L=\frac{wD}{2.44\lambda}\\L=\frac{0.12\times 10^{-3}\times 0 .01}{2.44\times 633 \times 10^{-9}}\\L=0.776 m[/tex]
