What is the intensity in w/m2 of a laser beam used to burn away cancerous tissue that, when 91.0% absorbed, puts 540 j of energy into a circular spot 2.60 mm in diameter in 4.00 s?

2.3x10⁷ W/m²

Explanation:

The intensity (I) of a laser is its potency (P) divided by the area (A) that it is affected. The potency is the energy applied (or absorbed) in a period, thus id 91.0% of the energy is absorbed, so:

E = 0.91*540 = 491.4 J

And,

P = E/t, where t is the time in seconds

P = 491.4/4.00

P = 122.85 J/s

P = 122.85 W

The are of a circular spot is:

A = (π/4)*d²

Where d is the diameter. Thus, with d = 2.60 mm = 0.0026 m

A = (π/4)*(0.0026)²

A = 5.31x10⁻⁶ m²

I = P/A

I = 122.85/5.31x10⁻⁶

I = 2.3x10⁷ W/m²

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.

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sio2 (quartz)