Question

LASIK eye surgery uses pulses of laser light to shave off tissue from the cornea, reshaping it. A typical LASIK laser emits a 1.0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 20 ns and contains 1.4 mJ of light energy.

a. What is the power of one laser pulse?
b. During the very brief time of the pulse, what is the intensity of the light wave?

Answer 1

Answer:

a.70000 W

b. 8.9 x $10^{10}$ W/m²

Explanation:

a. In order to find power of one laser pulse:

P= U/Δt

where,

U=light energy

Δt=laser pulse

P=1.4 x $10^{-3}$/20 x $10^{-9}$=>70000 W

b. Given:

Radius: 5 x $10^{-4}$

Intensity of light wave is given by

I= P/a (a=πr²)

where I is intensity and P is the power through an area a

I= 70000 /  π(5 x $10^{-4}$)²

I= 8.9 x $10^{10}$ W/m²

Answer 2

Answer:

a) 7*10^4 W

b) 8.91*10^10 W/m²

Explanation:

Given

Diameter of the beam, d = 1*10^-3 m

Wavelength of the beam, λ = 193 nm

Time of each pulse, t = 20 ns

Energy of each pulse, U = 1.4 mJ

Using the formula,

P = U/Δt

P = 1.4*10^-3 / 20*10^-9

P = 7*10^4 W

Again, using the formula,

I = P/a, where

a = πd²/4

a = 3.142 * (1*10^-3)²/ 4

a = 3.142 * 2.5*10^-7

a = 7.855*10^-7, thus

I = 7*10^4 / 7.855*10^-7

I = 8.91*10^10 W/m²

Therefore, the power of one laser pulse and the intensity of the light wave is 7*10^4 W and 8.91*10^10 W/m² respectively