A Laser Beam has Intensity Io?
A) What is the intensity, in terms of Io, if a lens focuses the laser beam to 1/10 its initial diameter? I=?
B) What is the intensity, in terms of Io, if a lens DEfocuses the laser beam to 10 its initial diameter?
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Intensity in this case is the beam power (P) per unit of area (A) .. I = P/A (W/m²)
For the same emitted power, the intensity is inversely proportional to the area
As area A ∝ d² ..
• d/10 reduces the area by a factor 100 .. ►intensity increases by a factor of 100
• 10d increases the area by a factor 100 .. ►intensity decreases by a factor of 100