No. of photons =(hc/λ)E=6.6×10−34×3×1089×10−3×6.67×10−7=3×1016
Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is :
Held on 30 Apr 2009 · Verified 9 Jul 2026.
3×1019
9×1017
3×1016
9×1015
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