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 2.0 mJ of light energy.

Part A: What is the power of one laser pulse?
Part B: During the very brief time of the pulse, what is the intensity of the light wave?

Answer 1

a) P = 1.0 10⁵ W, b) I = 1.27 10¹¹ W / m²

Step-by-step explanation:

a) the power is defined by the unit of time work

P = W / t

Work is equal to the variation of energy

P = E / t

Let's calculate

P = 2.0 10⁻³ / 20 10⁻⁹

P = 1.0 10⁵ W

b) intensity is defined as the ratio between power per area unit

I = P / A

The area of a circle is

A = π r²

r = d / 2

A = π (0.5 10⁻³)²

A = 0.785 10⁻⁶ m²

I = 1.0 10⁵ / 0.786 10⁻⁶

I = 1.27 10¹¹ W / m²