Which Metal Is Best for a Sensitive Light Meter Cathode?

AI Thread Summary
The discussion centers on determining the best metal for coating a sensitive light meter cathode to detect all colors of visible light. Sodium, cesium, and silver are evaluated based on their work functions and the corresponding wavelengths they can detect. Calculations show that silver has the highest sensitivity at 273 nanometers, while cesium and sodium follow at 576 and 454 nanometers, respectively. The conclusion suggests that cesium may be the most sensitive due to its lower frequency emission. Ultimately, the choice of metal depends on balancing sensitivity with the ability to respond across the visible light spectrum.
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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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