How Is Maximum Kinetic Energy Calculated in the Photoelectric Effect?

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SUMMARY

The maximum kinetic energy (Ek) of ejected electrons in the photoelectric effect can be calculated using the equation Ek = (hc/lambda) - W, where W is the work function. In this discussion, a magnesium surface with a work function of 3.68 eV and electromagnetic waves of wavelength 215 nm were analyzed. The correct calculation yields a maximum kinetic energy of 2.10 eV, highlighting the importance of accurate unit conversion and attention to significant figures in calculations.

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  • Understanding of the photoelectric effect and its principles
  • Familiarity with the equation Ek = (hc/lambda) - W
  • Knowledge of unit conversions between electron volts (eV) and joules (J)
  • Basic grasp of electromagnetic wave properties, including wavelength
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  • Study the derivation and implications of the photoelectric effect
  • Learn about unit conversions between eV and J, specifically for work functions
  • Explore the significance of wavelength in photon energy calculations
  • Investigate the role of different materials and their work functions in the photoelectric effect
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Students in physics, educators teaching photoelectric phenomena, and researchers exploring quantum mechanics and electron behavior in materials.

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Homework Statement


A magnesium surface has a work.func of 3.68eV. El.mag. waves with wavelength of 215nm strike the surface and eject electrons. Find the max Ek of the ejected electrons in eV.

Homework Equations


E=Ek-W <=> Ek=(hc/lambda) - W

The Attempt at a Solution


I convert eV to J and nm to m but i get -3.68*10^10eV, but the answer is suppoused to be 2.10eV.
I even re did it but got the same answer, where em I going wrong?

Thanks
 
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Hello.
In order to see where you are going wrong, we need to see your entire calculation.
 
Ek=(hc/lambda)-W

((6.63*10^-34)*(3*10^8))/(2.15*10^-7) - (5.888*10^-9)

(9.25*10^-19) - ( (5.888*10^-9) = -5.887*10^-9 J / (1.6*10^-19) = -3.68*10^10eV
 
mss90 said:
Ek=(hc/lambda)-W

((6.63*10^-34)*(3*10^8))/(2.15*10^-7) - (5.888*10^-9)

(9.25*10^-19) - ( (5.888*10^-9) = -5.887*10^-9 J / (1.6*10^-19) = -3.68*10^10eV

Check the power of 10 for the work function expressed in Joules.
 
ah ye, there we go. thanks :)
 

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