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Fusion is the process by which the sun produces energy. One experimental techniq

ID: 2122226 • Letter: F

Question


Fusion is the process by which the sun produces energy. One experimental technique for creating controlled fusion utilizes a solid-state laser that emits a wavelength of 1250 nm and can produce a power of 1.13E+14 W for a pulse duration of 1.10E-11 s. In contrast, the helium/neon laser used at the checkout counter in a bar-code scanner emits a wavelength of 633 nm and produces a power of about 1.30E-3 W. How long (in days) would the helium/neon laser have to operate to produce the same number of photons that the solid-state laser produces in 1.10E-11 s? Do not enter unit.

Explanation / Answer

for solid state laser

%u03BB=1250 nm = 1250*10-9 m

energy of 1 photon = hc/%u03BB = 1.8753*10-19 J

number of photons in 1 pulse = power produced*time/energy of 1 photon = 1.13*1014 * 1.1*10-11/1.8753*10-19

=6.628*1021

number of photons in1.10E-11 s?= 4.639*1022


now for neon laser

%u03BB=633 nm =  633*10-9 m

energy of 1 photon = hc/%u03BB = 3.14032*10-19 J

since number of photons=P*t/energy of 1 photon

=>4.639*1022 =1.3*10-3*t/ 3.14032*10-19 => t== 129.709 days