Question

Intensity at O due to the entire wavefront is x times that due to the first half period zone. What is x?

(a) 4

(b) 2

(c) 1/2

(d) 1/4

The question was asked by my school principal while I was bunking the class.

Question is taken from Fresnel Diffraction topic in division Optics of Engineering Physics II

Answer 1

Correct option is (d) 1/4

Best explanation: The formula for intensity = \(\frac{m_1^2}{4}\)

The intensity due to the first half period zone = m1^2

Thus, the intensity at O due to the entire wavefront is 1/4 times that due to the first half period zone.