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Lina20 [59]
3 years ago
15

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?
Physics
1 answer:
pickupchik [31]3 years ago
6 0

Answer:

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

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

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Explanation:

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A 70.0 kg sprinter starts a race with an acceleration of 1.60 m/s^2, What is the net external force (in N) on him? (Enter the ma
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Answer:

External force on him will be 112 N

Explanation:

We have given the mass of the sprinter m =70 kg

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You hang a heavy ball with a mass of 10 kg from a gold wire 2.6 m long that is 1.6 mm in diameter. You measure the stretch of th
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<u>Answer:</u> The Young's modulus for the wire is 6.378\times 10^{10}N/m^2

<u>Explanation:</u>

Young's Modulus is defined as the ratio of stress acting on a substance to the amount of strain produced.

The equation representing Young's Modulus is:

Y=\frac{F/A}{\Delta l/l}=\frac{Fl}{A\Delta l}

where,

Y = Young's Modulus

F = force exerted by the weight  = m\times g

m = mass of the ball = 10 kg

g = acceleration due to gravity = 9.81m/s^2

l = length of wire  = 2.6 m

A = area of cross section  = \pi r^2

r = radius of the wire = \frac{d}{2}=\frac{1.6mm}{2}=0.8mm=8\times 10^{-4}m      (Conversion factor:  1 m = 1000 mm)

\Delta l = change in length  = 1.99 mm = 1.99\times 10^{-3}m

Putting values in above equation, we get:

Y=\frac{10\times 9.81\times 2.6}{(3.14\times (8\times 10^{-4})^2)\times 1.99\times 10^{-3}}\\\\Y=6.378\times 10^{10}N/m^2

Hence, the Young's modulus for the wire is 6.378\times 10^{10}N/m^2

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