The beam emerging from a 1.5 W argon laser (l 515 nm) has a diameter d of 3.0 mm. The
Chapter 38, Problem 8(choose chapter or problem)
The beam emerging from a 1.5 W argon laser (l 515 nm) has a diameter d of 3.0 mm. The beam is focused by a lens system with an effective focal length fL of 2.5 mm. The focused beam strikes a totally absorbing screen, where it forms a circular diffraction pattern whose central disk has a radius R given by 1.22fLl/d. It can be shown that 84% of the incident energy ends up within this central disk. At what rate are photons absorbed by the screen in the central disk of the diffraction pattern?
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