A laser beam has intensity I (base 0). Part A: What is the intensity, in terms o

Question

A laser beam has intensity I (base 0).

Part A: What is the intensity, in terms of I, if a lens focuses the laser beam to 1/10 its initial diameter?

Part B: What is the intensity, in terms of I, if a lens defocuses the laser beam to 10 times its initial diameter?

Conceptual Question 15.14 Part A A laser beam has intensity Io What is the intensity, in terms of Io, if a lens focuses the laser beam to 1/10 its initial diameter? Io Submit My Answers Give Up Part B What is the intensity, in terms of Io, if a lens defocuses the laser beam to 10 times its initial diameter? Io Submit My Answers Give Up

Explanation / Answer

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

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