Unformatted text preview: Assignment 1 How many photons/sec are in a continuous 10 Watt laser beam having
a) blue light 514 um b) red light 650 nm. How long does it take to raise 1 liter of water by 10° C when it fully absorbs a
10 Watt laser beam? Assume that no heat is lost through the top, bottom or
sides of the container. Laser cooling refers to slowing or stopping a moving atom by directing a laser
at it. The atom loses momentum whenever it absorbs an oncoming photon.
Subsequently, the photon is reradiated in no preferred direction. a) Estimate the number of photons (it = 780 nm) required to stop a rubidium
atom initially moving at the speed of sound. b) How long does it take to st0p one atom if it takes about 25 nsec before the
excited atom reradiates the photon? c) What distance does the atom travel while the laser slows it down to a
stop? d) How much laser power is required to stop an atomic beam having 1
billion atoms/sec? Estimate the time for light to travel from Toronto to Paris via
a) an optical ﬁber under the ocean b) via a satellite in geosynchronous orbit A computer disk is made by focusing light to a spot whose diameter is
comparable to the optical wavelength. Find the number of bits that can be
stored on a 10 cm diameter optical disk using a) an infrared laser b) an ultraviolet laser. ...
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- Winter '10