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An LED that emits light of wavelength λ = 667 nm illuminates the phototube. A reverse bias is applied to the phototube (a voltage that opposes the current flow). This is adjusted carefully until the photocurrent drops to zero. The stopping potential is found to be Vo = 0.43 V.The LED can now be changed and the process repeated for a different λ. Then the data can be plotted to determine Planck's constant, h.For the data collected above what value would you plot on the x-axis of your graph? (Use c = 3.00 x 108m/s.)Express your answer in SI units to 3 significant figures.Entering numbers in scientific notation: Example: 1.45 x 10-9 should be entered as 1.45E-9

Question

An LED that emits light of wavelength λ = 667 nm illuminates the phototube. A reverse bias is applied to the phototube (a voltage that opposes the current flow). This is adjusted carefully until the photocurrent drops to zero. The stopping potential is found to be Vo = 0.43 V.The LED can now be changed and the process repeated for a different λ. Then the data can be plotted to determine Planck's constant, h.For the data collected above what value would you plot on the x-axis of your graph? (Use c = 3.00 x 108m/s.)Express your answer in SI units to 3 significant figures.Entering numbers in scientific notation: Example: 1.45 x 10-9 should be entered as 1.45E-9

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Solution

The x-axis of your graph should be the frequency of the light emitted by the LED. The frequency can be calculated using the formula:

f = c / λ

where: f is the frequency, c is the speed of light (3.00 x 10^8 m/s), and λ is the wavelength (667 nm = 667 x 10^-9 m).

Substituting the given values into the formula gives:

f = (3.00 x 10^8 m/s) / (667 x 10^-9 m) = 4.49 x 10^14 Hz

So, the value you would plot on the x-axis of your graph is 4.49 x 10^14 Hz.

This problem has been solved

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