How Many Photons Are Emitted by a 100W Bulb per Second?

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SUMMARY

The discussion centers on calculating the number of photons emitted by a 100W bulb, specifically for visible light at a wavelength of 500 nm. The consensus is that approximately 1020 photons are emitted per second, although one participant calculated a slightly higher value of 2.5 x 1020 photons/second. The calculations utilize the relationship between energy, power, and the energy of individual photons, defined by the equation E=hf. This highlights the importance of precise calculations in physics problems.

PREREQUISITES
  • Understanding of the equation E=hf for photon energy
  • Knowledge of the relationship between power, energy, and time (E=P*t)
  • Familiarity with the concept of wavelength in the electromagnetic spectrum
  • Basic proficiency in scientific notation and calculations
NEXT STEPS
  • Research the implications of photon emission in different types of light bulbs
  • Learn about the Planck constant (h) and its role in photon energy calculations
  • Explore the relationship between wavelength and energy in the context of the electromagnetic spectrum
  • Investigate how variations in bulb efficiency affect photon output
USEFUL FOR

Students studying physics, particularly those focusing on optics and energy, as well as educators looking for practical examples of photon calculations.

Brammo
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Homework Statement



Estimate how many photons of visible light (500 nm) are emitted by a 100 W Bulb.

The answer on the sheet says approximately 10^{20} photons/second

However when I work it out I get a slightly different answer.

Homework Equations



I used that 1J=1W/s or E=P/t

Also Energy of one photon is E=hf so if you had lots of photons you would \DeltaE=nhf where n is the number of photons.

The Attempt at a Solution



I get 2.5\times10^{20} photons/second
 
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You solved the problem correctly.
 

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