Question

Measured Wavelength for Hg vapor

> 900 3. A student used a Measured Wavelength (nm) vs. Actual Wavelength (nm) for Hg Vapor spectroscope to view the emission spectrum of Hg vapor, and plotted her measured wavelengths ly- axis) vs. the actual wavelengths (x-axis). The actual wavelength of the most prominent line in the emission spectrum of Na is 589 nm. If the spectroscope used to prepare the calibration curve is used to view the emission spectrum of Na, what wavelength would be measured for this line?! Page 1 of 2

Answer 1

From the plot of measured wavelength vs actual wavelength, we can calculate the measured wavelength of a line with actual wavelength = 589 nm as follows:

For us the actual wavelength of the most prominent line of Na emission spectrum is at 589 nm.

Hence, we draw a vertical line at x = 589 until it touched the graph line.

Then, we draw a horizontal line to y axis from the point where the vertical line meets the graph. This way we find the value of y in the y axis for which x = 589 nm.

Measured Wavelength (nm) vs. Actual Wavelength (nm) for Hg Vapor 750 700 650 600 550 500 450 400 350 500 550 600 650 350 400 450 700 Actual Wavelength (nm) Measured Wavelength (nm)

Looking at the graph, the horizontal line touches the y axis at y = 600 nm approximately.

Note that y axis represent the measured wavelength, hence, the measured wavelength for the Na line is about 600 nm approximately.

Note: if the data points taken for the graph are exactly known, we can calculate the value mathematically.