Question

For an aperture of size a illuminated by a parallel beam of light having wavelength $ \lambda , $ the Fresnel distance is

• A. $ \approx a/\lambda $
• B. $ \approx a^{2}/\lambda $
• C. $ \approx a^{2}\lambda $
• D. $ \approx a/\lambda ^{2} $

Answer 1

Answer: (B)

In this case, the Fresnel distance is equavelent to $a^{2}/\lambda $