Which Metal Is Best for a Sensitive Light Meter Cathode?

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SUMMARY

The best metal for coating the cathode of a light meter to ensure sensitivity across the visible spectrum (400 nm to 700 nm) is Silver, with a work function of 4.73 eV, resulting in a threshold frequency that allows detection of light wavelengths down to 273 nm. While Sodium (2.75 eV) and Cesium (2.14 eV) have lower work functions, their corresponding threshold frequencies (454 nm and 576 nm, respectively) make them less effective for visible light sensitivity. The calculations confirm that Silver is optimal for this application due to its ability to respond to a broader range of light wavelengths.

PREREQUISITES
  • Understanding of the photoelectric effect and its equations
  • Familiarity with work function and threshold frequency concepts
  • Knowledge of Planck's constant and its application in calculations
  • Basic principles of light wavelength and energy relationships
NEXT STEPS
  • Research the properties and applications of Silver in photodetectors
  • Explore the photoelectric effect in depth, focusing on work function variations
  • Learn about alternative materials for light-sensitive applications, such as Gallium Arsenide
  • Investigate the impact of different metals on the efficiency of light meters
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Students and professionals in physics, materials science, and optical engineering who are interested in the design and optimization of light-sensitive devices.

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Homework Statement



Out of Sodium (2.75 eV), Cesium (2.14 eV) and Silver (4.73 eV), which metal would be best suited to coat the cathode of the light meter such that it is sensitive to all colors of light? The range of wavelength for visible light is 700 nm to 400 nm.

Homework Equations



threshold frequency= work function/ planks constant 4.14x10^-15
Hz= speed of light/ threshold frequency

The Attempt at a Solution



2.75/4.14x10^-15= 6.6x10^-16= 3x10^8/6.6x10^-16= 4.5 nanometers
2.14/4.14x10^-15= 5.2x10^-16= 3x10^8/5.2x10^-16= 5.8 nanometers
4.73/4.14x10^-15= 1.1x10^-15=3x10^8/1.1x10^-15= 273 nanometers

silver is the closest to being sensible to colors of light.

it seems to me like i did everything right but nothing goes to sensible light, and i don't know what I am doing wrong
 
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For the photoelectric effect isn't it:

hf = φ + Ekmax

where φ = h*fo
and E is the kinetic energy of the electrons freed up.

So then it seems that the energy of the incident light times Plank and the frequency of the light would be your budget and the closer your work function φ is to the visible light spectra then the less that is available for the Ekmax.
 
alright. i got the calculations now,
silver= 273 nanometers
cesium= 576 nanometers
sodium= 454 nanometers
would cesium be the most sensitive one because it emits the least frequency?
 

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