Laser beams are sometimes used to burn away cancerous tissue. show answer Incorrect Answer What is the intensity, in watts per square meter, of a laser beam that is 90.0% absorbed by a 1.95-mm diameter spot of cancerous tissue and must deposit 495 J of energy to it in a time period of 3.8 s

The intensity of the beam is

Explanation:

We can find the intensity absorbed by the spot cancerous tissue with the equation:

(1)

with P average power and A the effective area. Average power is the energy (E) absorbed in a certain time (t) so:

(2)

Using (2) on (1)

(3)

We can assume the area of the spot as a circumference of radius (r) 1.95 mm or so the area of a circumference with this radius is:

Using this value on (3)

(3)

Because the tissue only absorbs 90% of the intensity the total intensity, we can use the relation:

to find the intensity of the beam (I):

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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