Question

In a laser cavity transmission voefficient is 0.01, wavelength is 694 nm , length is 10 cm power is 3mW. then no of photons is​

Answer 1

Answer:

Explanation:

Hecht, problem 9.20:

In the Fresnel double mirror, λ0 = 589 nm, the distance of the screen from the two virtual sources (Fig.

9.12) is s = 2 m, R = 1 m, and the separation of fringes is Δy = 0.5 mm. Determine the inclination angle

α between the mirrors.

From the sketch in Fig. 9.12a, the angle to S1 and S2, as seen from the intersection point of the two mirrors, O, is ∠(S1,O,S2) = 2α. (This can be shown by drawing the geometry around point O or, more easily, by the following physics argument: If α = 0, i.e., both mirrors line up, then S1 = S2 and thus

∠(S1,O,S2) = 0; if we then increase the tilt of mirror 2 against mirror 1 by Δα, then the reflection from

mirror 2, and therefore also the direction toward S2 is rotated by 2Δα around point O, leading to

∠(S1,O,S2) = 2Δα.)

Thus, sinα = a 2R . On the other hand, Δy ≈ sλ a , so

sinα = sλ

2ΔyR , or α = 0.0018 (in rad) = 0.067°.