Asked Dec 8, 2019

How many photons are there in a 7.00 mJ laser beam of wavelength 785 nm?


Expert Answer

Step 1

Energy is converted to joules as shown below:

1 mJ = 10-3 J

7mJ  = 0.007 J

The relation between number of photons, wavelength and energy is shown below:


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nhc E, (1)

Step 2

Wavelength is converted int...


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1 nm =10° m 785 nm = 785×10-°m


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