Experiment 16: Color and Spectra

Purpose: To observe the color spectra of white light and to measure the wavelengths of several different colors. We will investigate light spectra further by measuring wavelength of light emitted by a hydrogen tube.

Materials:

• discharge tube
• power supply
• incandescent lamp
• meter sticks
• markers
• diffraction grating
• grafting holder
• hydrogen tube

Set Up:

The wavelength measuring apparatus is set up as shown. Two rulers are set up making a right angle at the light source. A person can view the light spectrum through the diffraction grating. We can measure the wavelength by marking the beginning and end of the spectrum on the ruler.

Experiment:

First we calculated the average wavelength and standard deviation of the true values of the spectra found by other experimentalists.

Then we measured the values ourselves by looking through the diffraction grating and marking the beginning and end of the spectrum. Each trial was measured by a different person.

Now we could calibrate our equation for viewing of the hydrogen spectra

Our calibrated equation is y = 1.0699 x - 58.43

After obtaining measurements for the hydrogen gas spectra we can plug the values into this equation.

For the purple wavelength we calculated the value to be 381.3 +- 12.5 nm. The actual value from the Balmer series is 410. Substitute into the calibration equation and get 380.23 nm

For the blue wavelength we calculated the value to be 449.8 +- 15.0 nm. The actual value from the Balmer series is 486 nm. Substitute into the calibration equation and get 461.54 nm

For the red wavelength we calculated the value to be 622.0 +- 5.5 nm. The actual value from the Balmer series is 656 nm. Substitute into the calibration equation and get 643.42 nm

Conclusion: Based off these measurements are percent error for the purple wavelength was 0.28%, 2.54% for blue wavelength, and 3.33% for red wavelength. These measurements are therefore fairly accurate.