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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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Art [367]
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8 0
3 years ago
A Gaussian surface in the form of a hemisphere of radius R = 3.04 cm lies in a uniform electric field of magnitude E = 1.64 N/C.
Likurg_2 [28]

Answer:

Part a)

\phi = -4.76 \times 10^{-3} Nm^2/C

Part b)

\phi_{curved} = 4.76 \times 10^{-3} Nm^2/C

Explanation:

Part a)

Electric flux entering into the base

so it is given as

\phi = E.A

\phi = - EA

\phi = -(1.64)(\pi r^2)

\phi = -(1.64)(\pi\times 0.0304^2)

\phi = -4.76 \times 10^{-3} Nm^2/C

Part b)

Now since we know that there is no enclosed charge in the hemisphere

so net flux must be zero

\phi_{curved} + \phi_{flat} = 0

\phi_{curved} - 4.76 \times 10^{-3} = 0

\phi_{curved} = 4.76 \times 10^{-3} Nm^2/C

7 0
2 years ago
8.)The potential energy of a 40-kg cannonball is 14000 J. How high was the cannon ball to have this much potential energy?
Delvig [45]

Hey! I empathize with you, as I just started the energy unit in physics as well!

Alright, lets list what we know, and which equation(s) we need.

PE = Gravitational Potential Energy

PEg = mgh

m = mass

g = gravity (9.8 m/s^2)

h = height

Guess what?

We need to find the height!

Lets make this more organized:

Known:

m = 40 kg

PE = 14000

g = 9.8 m/s^2

Unknown:

h = ?

================================

Now, if we take a look at the equation PEg = mgh, you will see that we have everything besides the height! So lets solve for the height by substituting in for the variables we know:

14000 J = 40 kg * (9.8 m/s^2) * h

40 * 9.8 = 392  

14000 J = 392 * h

14000/392 = h

35.71 m = h

There we go! If you simply list what you know and don't know, you will find the equation you need to solve the problem.

Have a great day and good luck!

7 0
3 years ago
How do scientists know the continents were once closer than they are today? Explain your answer in 2-3 complete sentences.
WITCHER [35]

Answer:

Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics. 

 

The theory of continental drift is most associated with the scientist Alfred Wegener. In the early 20th century, Wegener published a paper explaining his theory that the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other. He called this movement continental drift. 

6 0
3 years ago
True or false? All waves need a medium in order to travel
Art [367]
That's false.  Mechanical waves (like sound and ocean waves) do
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4 0
3 years ago
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