Chapter 39: Problem 32
Pulsed dye lasers emit light of wavelength 585 nm in 0.45-ms pulses to remove skin blemishes such as birthmarks. The beam is usually focused onto a circular spot 5.0 mm in diameter. Suppose that the output of one such laser is 20.0 W. (a) What is the energy of each photon, in eV? (b) How many photons per square millimeter are delivered to the blemish during each pulse?
Short Answer
Step by step solution
Calculate the Energy of a Photon
Calculate the Total Energy in One Pulse
Calculate the Number of Photons per Pulse
Calculate the Area of the Laser Spot
Calculate Photons per Square Millimeter
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Photon Energy
- \( h = 6.626 \times 10^{-34} \text{ J s} \) is Planck's constant, a universal constant that plays a central role in quantum mechanics.
- \( c = 3.00 \times 10^8 \text{ m/s} \) is the speed of light, another fundamental constant.
- \( \lambda \) is the wavelength of the light. For the problem at hand, the wavelength is 585 nm, which we convert to meters (\( 585 \times 10^{-9} \text{ m} \)).