Radiation pressure of a light bulb

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SUMMARY

The discussion focuses on estimating the radiation pressure produced by a 100 W light bulb at a distance of 8.4 cm. The relevant equations include the relationship between power, force, and distance, as well as the calculation of pressure using the Poynting vector divided by the speed of light. The derived formula for force is F = Power/c, leading to the conclusion that pressure can be expressed as Intensity/c. It is critical to note that this calculation assumes the light is absorbed; reflected light would result in double the pressure.

PREREQUISITES
  • Understanding of basic physics concepts such as power, force, and pressure
  • Familiarity with the Poynting vector and its application in electromagnetic theory
  • Knowledge of the speed of light and its significance in radiation pressure calculations
  • Ability to perform calculations involving spherical geometry, specifically the area of a sphere
NEXT STEPS
  • Research the Poynting vector and its role in electromagnetic radiation
  • Learn about the effects of light reflection on radiation pressure
  • Explore the concept of intensity in the context of light and its relation to power
  • Investigate practical applications of radiation pressure in various fields of physics
USEFUL FOR

Students studying physics, particularly those interested in electromagnetism, as well as professionals working in optics and photonics who require a deeper understanding of radiation pressure phenomena.

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1. Homework Statement
Estimate the radiation pressure due to a 100 W bulb at a distance of 8.4 cm from the center of the bulb.

2. Relevant equations
Power= Work/Time W=Force(distance)

Pressure = Force/Area = Poynting vector/speed of light

3. The Attempt at a Solution
I found the cross sectional area by doing 4∏ r^2, so I have that. Then, seeing as I was given power and distance, I tried to figure out the Force in terms of Power and distance, but in doing that, I got the formula F= Power (Time)/distance, and I wasn't given the time. Is there some formula that I'm missing?
 
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distance/Time is velocity ... so your "(Time)/distance" = 1/c .
This means that your F= Power/c ... Pressure = Intensity/c .

Note that this is only true if the 100W of light is absorbed
(light being reflected would double the pressure)
 

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