question_answer

A laser light of wavelength 660 nm is used to weld Retina detachment. If a laser pulse of width 60 ms and power 0.5 kW is used the approximate number of photons in the pulse are - [JEE Online 09-04-2017]

[Take Planck's constant \[h=6.62\,\times {{10}^{-34}}Js\]]

A) \[{{10}^{22}}\]       

B) \[{{10}^{19}}\]

C) \[{{10}^{20}}\]       

D) \[{{10}^{18}}\]

Correct Answer: C

Solution :

[c]