Question 193: Dual Nature of Matter and Radiation

Question

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 :
[Take Planck's constant h $$=$$ 6.62 $$ 	imes $$ 10
$$-$$34
Js]

Accepted Answer

The power of the given laser light is expressed as
$$P = {{nhc} \over {\lambda t}}$$
from which the number of photons per second is given by
$$n = P\left( {{{\lambda t} \over {hc}}} ight) = (5 	imes {10^2}) 	imes \left[ {{{(660 	imes {{10}^{ - 9}})(60 	imes {{10}^{ - 3}})} \over {(6.6 	imes {{10}^{ - 34}})(3 	imes {{10}^8})}}} ight]$$
$$ = 100 	imes {10^{18}} = {10^{20}}$$

Answer

10
20

Answer

10
18

Answer

10
22

Answer

10
19

Dual Nature of Matter and Radiation

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 : [Take Planck's constant h $= 6.62 \times 10 -$34 Js]

Choose the correct answer: