Work Function Questions - Help Bob Find the Answer

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SUMMARY

The discussion centers on Bob's confusion regarding the calculation of work functions in the context of photoelectric effect. Bob uses the equation ø = hf - 0.5mv², where he substitutes values for wavelength, speed of ejected electrons, and constants. However, he arrives at a negative work function value, indicating a miscalculation. A participant suggests that Bob may have omitted the speed of light (c) in his calculations, which is crucial for converting wavelength to frequency.

PREREQUISITES
  • Understanding of the photoelectric effect and work function
  • Familiarity with the equation ø = hf - 0.5mv²
  • Knowledge of constants such as Planck's constant (h) and electron mass (m)
  • Ability to convert wavelength to frequency using the speed of light (c)
NEXT STEPS
  • Learn about the photoelectric effect and its implications in quantum mechanics
  • Study the derivation and application of the equation ø = hf - 0.5mv²
  • Explore how to convert wavelength to frequency using the formula f = c/λ
  • Investigate common mistakes in work function calculations and how to avoid them
USEFUL FOR

Students and researchers in physics, particularly those studying quantum mechanics and the photoelectric effect, as well as educators looking to clarify concepts related to work functions.

bobbles22
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Hi all,

I'm trying to understand work functions and am working through a paper but keep coming up with the wrong answer. Can anyone point out where I'm going wrong please...

Wavelength of light incident on surface = 560 nm
Max speed of ejected electrons = 1.67 x 105 ms-1
1 eV = 1.602 x 10-19 J

I'm using 0.5mv2=hf-ø rearranged as ø=hf-0.5mv2

Putting in the figures above:

=(6.63 x 10-34) x (1 / (5.6 x 10-19)) - 0.5 (1.67 x 105)2 x 9.109 x 10-31

= 1.18 x 10-27 - 12.70 x 10-21 = -1.27 x 10-20 J

I'm sure I'm not meant to come up with a negative answer.

Many thanks for any assistance you can give.

Bob
 
Physics news on Phys.org
Hi Bob, shouldn't there be a c in there?
 

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