Figure shows a beam expander made with two coaxial converging lenses of focal lengths f1 and f2 and separation d = f1 + f2. The device can expand a laser beam while keeping the light rays in the beam parallel to the central axis through the lenses. Suppose a uniform laser beam of width Wi =2.5 mm and intensity Ii = 9.0 kW/m2 enters a beam expander for which f1 = 12.5 cm and f2 = 30.0 cm. What are?

(a) Wf and

(b) If of the beam leaving the expander?

(c) What value of d ts needed for the beam expander if lens I is replaced with a diverging lens of focal length f1 = ?? 26.0cm?

Transcribed Image Text:

W, 2 W