Question

The numerical aperture of a material with acceptance angle of 60 degree in water will be (a) 1.15 (b) 2.15 (c) 5.21 (d) 1.52 This question was posed to me by my college director while I was bunking the class. My doubt stems from Refractive Index and Numerical Aperture topic in division EM Wave Propagation of Electromagnetic Theory Select the correct answer from above options Electromagnetic Theory questions and answers, Electromagnetic Theory questions pdf, Electromagnetic Theory question bank, Electromagnetic Theory questions and answers pdf, mcq on Electromagnetic Theory pdf,electromagnetic theory book pdf,electromagnetic theory pdf notes,electromagnetic theory lecture notes,electromagnetic theory of light,maxwell electromagnetic theory,electromagnetic theory proposed by,electromagnetic theory engineering physics,electromagnetic theory nptel

Answer 1

The correct answer is (a) 1.15 The explanation is: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is 1.33 for water medium. Given that the acceptance angle is 60, we get NA = 1.33 sin 60 = 1.15.