Балкански 2009, Теория — Задача 2. Exercise 1

Concours Général de Physiques « Minko Balkanski » · 16 май 2009 г. · 3 т.

Указания

The main problem and the two exercises are completely independent and can be solved in any order.

All the answers must be given in English or French. The clarity and precision will be taken into account for the final note.

The exam is 4 hours long! The calculators are authorized.

Условие

A plano-concave lens having index of refraction $n = 1{,}50$ is placed on a flat glass plate, as shown in Figure 1. Its curved surface, with radius of curvature 8.00 m, is on the bottom. The lens is illuminated from above with yellow sodium light of wavelength 589 nm, and a series of concentric bright and dark rings is observed by reflection. The interference pattern has a dark spot at the center, surrounded by 50 dark rings, of which the largest is at the outer edge of the lens.

(a) What is the thickness of the air layer at the center of the interference pattern?

(b) Calculate the radius of the outermost dark ring.

(c) Find the focal length of the lens.

Решение

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Оригинал в Архива: CGP_2009_en.pdf