A: Calculating Photon Count from Electrical Energy and Efficiency

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SUMMARY

The discussion focuses on calculating the photon count emitted by a sixty-watt incandescent light bulb operating at 2.2% efficiency, specifically for green light at a wavelength of approximately 5500 Å. To determine the number of photons per second, participants must first calculate the energy produced in visible light and the energy per photon using the equation E=hf, where h is Planck's constant. The second part of the problem involves calculating how many photons enter the eye when standing 3.5 meters away from the bulb for 0.10 seconds, considering the pupil diameter of 2.1 mm.

PREREQUISITES
  • Understanding of Planck's constant (h) and its application in photon energy calculations
  • Knowledge of wavelength conversion from angstroms to meters
  • Familiarity with the efficiency of light bulbs and energy conversion
  • Basic principles of light propagation and geometry related to pupil size
NEXT STEPS
  • Calculate photon energy using E=hf for various wavelengths
  • Explore the efficiency of different types of light bulbs, such as LED and fluorescent
  • Investigate the effects of distance on light intensity and photon count
  • Learn about the human eye's response to light and photon detection
USEFUL FOR

Students in physics or engineering, educators teaching optics, and anyone interested in the practical applications of light energy calculations.

wildredhead
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Homework Statement


In converting electrical energy into light energy, a sixty-watt incandescent light bulb operates at
about 2.2% efficiency. Assuming that all of the light is green light (wavelength approximately
5500 Å), determine the number of photons per second given off by the bulb and B:if you were to look directly at the bulb, the light
from it would travel directly to your eye without reflecting from anything. If you stand 3.5
meters away and look at the bulb for only 0.10 seconds, how many photons will enter your eye?
(assume the pupil of your eye has a diameter of 2.1 mm)


Homework Equations


I don't really know what to use.
I think E= hf


The Attempt at a Solution


First I converted angstroms to wavelength then I found frequency. From frequency and planks constant I found E but then I got nothing . DOn't even know how to touch B.
 
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For (A), you need to answer two questions first:

1. How many Joules per second are produced in the form of visible light?

2. How many Joules of energy are in one photon? (Use the answer you got from using E=hf)
 

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