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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