A student investigates the consistency of laboratory measurements with the accepted…
PHYSICS · Multi-part · A Level · Physics · Measurements and their errors · Measurements and their errors
Problem
A student investigates the consistency of laboratory measurements with the accepted physical constant for the speed of light in a vacuum. Three spectral lines from an unknown element are analyzed. For each line, the wavelength is measured with a diffraction grating, and the frequency is obtained independently with a fast photodiode circuit. The results are summarized below.
Spectral Line
Measured Wavelength (nm)
Measured Frequency (×1014Hz)
A
410
7.32
B
520
5.77
C
610
4.93
Answer the following questions about the data set.
(a) For each spectral line, calculate the product of the measured wavelength and frequency. Express each product in m⋅Hz, using scientific notation.
(b) Compute the average value of the three products obtained in part (a).
(c) The accepted value for the speed of light in a vacuum is 2.998×108ms−1. Determine the percent deviation of the student’s average value from the accepted value. Show all work.
(d) Discuss two plausible experimental sources of error that could account for the deviation calculated in part (c), and explain qualitatively how each source of error would influence the measured wavelength or frequency.