Question

The source is at some distance from an obstacle. Distance between obstacle and the point of observation is $b$ and wavelength of light is $\lambda$. Then the average distance of nth Fresnel zone will be at a distance from the point of observation

• A. $\frac{bn \lambda}{2}$
• B. $b-\frac{n \lambda}{2}$
• C. $b + \frac{n \lambda}{2}$
• D. $b - n \lambda$

Answer 1

Answer: (C)

$b + \frac{n \lambda}{2}$

Answer 2

The average distance of $n$th Fresnel zone from observation point wilI be at a distance $b + \frac{n \lambda}{2}.$