LASIK Laser 1 2 3 45 LASIK is a corrective surgical procedure intended to reduce

Question

LASIK Laser 1 2 3 45 LASIK is a corrective surgical procedure intended to reduce a person's dependency on glasses or contact lenses by actually modifying the shape of the cornea, the clear covering of the front of the human eye. LASIK stands for Laser- Assisted In Situ Keratomileusis and can use a laser to both shape the cornea and to assist in positioning the cornea for the correction. The laser involved is referred to as an Excimer laser, which use mixutures of both reactive gases (e.g. chlorine) and inert gases (e.g. argon) to produce lightly focused light in the ultra-violet spectrum. A typical laser might emit light in short pulses, 85 times per second, with each pulse lasting 10 nsec. The laser is referred to as a Icool lasert', which means that it does not heat up the surrounding air or surfaces. Instead, the very tightly-focused beam is absorbed by the upper layer of the surface that it contacts. Each pulse will deliver a total energy of 2.4 mJ. The light will with a wave length of 230 nm and the beam will have a diameter of approximately 0.9 mm. The sheer amount of ultraviolet light is too much for most organic materials (such as the cornea of the eye) to absorb, resulting in the breakdown of the molecular bonds of the material 1) What is the speed of this electromagenetic wave from the laser? m/s Submit Help 2) What is the frequency of this wave? Hz Submit Help 3) What is average power during each pulse? Ppuise w Submit

Explanation / Answer

1)The speed of electromagnetic wave is always same and equal to

v = 3 x 10^8 m/s

2)We know that

v = f lambda => f = v/lambda

f = (3 x 10^8)/(230 x 10^-9) = 1.304 x 10^15 Hz

Hence, f = 1.304 x 10^15 Hz

3)P = E/t

P = 2.4 x 10^-3/(10 x 10^-9) = 2.4 x 10^5 W

Hence, P = 2.4 x 10^5 W

4)We know that

I = P/A

I = 2.4 x 10^5/[3.14 x (0.45 x 10^-3)^2] = 3.77 x 10^11 W/m^2

Hence, I = 3.77 x 10^11 W/m^2

5)P = E/t

P = 2.3 x 10^-3/1 = 2.3 x 10^-3W

HEnce, P = 2.3 x 10^-3 W

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