Question

A laser used in LASIK eye surgery produces 55 pulses per second. The wavelength is 196.0 nm (in air), and each pulse lasts 21.1 ps. The average power emitted by the laser is 120.0 mW and the beam diameter is 0.800 mm. How long (in centimeters) is a single pulse of the laser in air?

Answer 1

Given that

= 196 nm = 196*10^-9 m

t = 21.1ps = 21.1*10^-12 s

P_avg = 12 mW

d = 0.8 mm = 0.8*10^-3 mm

r = d/2 = 0.4*10^-3 m

As we know that frequency of the laser pulse is equal to the velocity of the light divided by the wavelength of the laser pulse .

f = c/

f = 3*10⁸/196*10^-9

f = 1.53*10¹⁵ Hz

The frequency is lies in the ultra violet region of the electromagnetic spectrum .

The distance travelled by the laser pulse is,

d = c*t

d = 3*10⁸ * 21.1*10^-12

d = 6.33*10^-3 m

d = 6.33 mm