An LED that emits light of wavelength λ = 449 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 = 1.086 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 = 449 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 = 1.086 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
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:
Frequency (f) = Speed of light (c) / Wavelength (λ)
Given that the speed of light (c) is 3.00 x 10^8 m/s and the wavelength (λ) is 449 nm (which is 449 x 10^-9 m), you can substitute these values into the formula to find the frequency.
f = (3.00 x 10^8 m/s) / (449 x 10^-9 m)
After calculating, you should express your answer in SI units (Hz) to 3 significant figures.
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