The slope of the stopping voltage versus frequency graph was found to be m = 3.78 x 10-15 Vs. Use this value to determine Planck's constant.Express you answer to 3 significant figures in SI units. (Use a value of e = 1.6 x 10-19C for the charge on an electron.)Entering numbers in scientific notation: Example: 1.45 x 10-9 should be entered as 1.45E-9
Question
The slope of the stopping voltage versus frequency graph was found to be m = 3.78 x 10-15 Vs. Use this value to determine Planck's constant.Express you answer to 3 significant figures in SI units. (Use a value of e = 1.6 x 10-19C for the charge on an electron.)Entering numbers in scientific notation: Example: 1.45 x 10-9 should be entered as 1.45E-9
Solution
The slope of the stopping voltage versus frequency graph is equal to Planck's constant divided by the charge of an electron. This is a result of the photoelectric effect equation, which is:
V = h*f/e
where V is the stopping voltage, h is Planck's constant, f is the frequency, and e is the charge of an electron. Rearranging this equation for h gives:
h = V*e/f
The slope of the V versus f graph (m) is equal to h/e, so we can solve for h by multiplying the slope by the charge of an electron:
h = m*e
Substituting the given values gives:
h = (3.78 x 10^-15 Vs) * (1.6 x 10^-19 C)
= 6.05 x 10^-34 Js
So, Planck's constant is approximately 6.05 x 10^-34 Js to three significant figures.
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