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 sec. on the average at a target irradiated by this beam is
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 sec. on the average at a target irradiated by this beam is
- [AIPMT 2009]
- A
$3 \times 10^{16}$
- B
$9 \times 10^{15}$
- C
$3 \times 10^{19}$
- D
$9 \times 10^{17}$
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