Interference, Diffraction, and Spectra Name:________________________
Course:_______________Time:__________________Partners:____________________________
A. Visit this Two-Slit Interference website and answer the following questions:
1. What is the range of wavelength used in this applet?_____________________
2. As the wavelength is increased, describe what happens to the interference pattern?
_______________________________________________________________
3. What is the range of slit separation used in this applet?_________________________
4. Express the above range of slit separation in nanometers._______________________
5. As the slit separation is increased, describe what happens to the interference pattern?
_______________________________________________________________
6. Set the slit separation to 15 micrometers and wavelength to 600 nanometers. How far apart are the dark fringes?____________________
7. Express the above distance as angular width in radians. ____________________
B. Visit this Single-Slit Diffraction website and answer the following questions:
1. What is the range of wavelength used in this applet?_____________________
2. As the wavelength is increased, describe what happens to the diffraction pattern?
_______________________________________________________________
3. What is the range of slit width used in this applet?_________________________
4. Express the above range of slit width in nanometers._______________________
5. As the slit width is increased, describe what happens to the diffraction pattern?
_______________________________________________________________
6. Set the slit width to 20 micrometers and wavelength to 600 nanometers.
How wide is the central maximum ?____________________
How wide is the other maximum?______________________
C. Visit this Bohr Atom website and answer the following questions:
1. What is a Bohr atom?______________________________________________
2. What do the numbers next to the buttons on the right mark?
_________________________________________________________________
3. How are the electron orbits shown?____________________________________
4. What is the wavelength range in nm of the visible spectrum?___________________
5. To find out the transitions to which electron orbit will result in the visible spectra (Balmer series):
| a. Select the first button. | Click on the second electron orbit and observe the
wavelength of the line emitted. Is this a visible
line?____ Click on the third electron
orbit and observe the wavelength of the line emitted. Is this a visible
line? ________ Click on the fourth electron orbit and observe the wavelength of the line emitted. Is this a visible line? _______ Click on the fifth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the sixth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the seventh electron orbit and observe the wavelength of the line emitted. Is this a visible line? _____ Click on the eight electron orbit and observe the wavelength of the line emitted. Is this a visible line? _______ |
| b. Select the second button. | Click on the third electron orbit and observe the
wavelength of the line emitted. Is this a visible line? ________ Click on the fourth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the fifth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the sixth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the seventh electron orbit and observe the wavelength of the line emitted. Is this a visible line? _____ |
| c. Select the third button. | Click on the fourth electron orbit and observe the
wavelength of the line emitted. Is this a visible line? ________ Click on the fifth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the sixth electron orbit and observe the wavelength of the line emitted. Is this a visible line? ________ Click on the seventh electron orbit and observe the wavelength of the line emitted. Is this a visible line? _____ |
6. Make sure that the second button is selected. Click on the third electron orbit. You will see the electron transition from third electron orbit to the second electron orbit resulting in a red line emission. Record the wavelength (8) and change in energy ()E) in the data table. Repeat this for other electron orbits and complete the data table. You will complete the last column when you do the measurement with the Ocean Optics spectrometer.
| Transition from | )E | 8, from website | 8, measured | 8, Calculated |
| 3rd electron orbit | ||||
| 4th electron orbit | ||||
| 5th electron orbit | ||||
| 6th electron orbit | ||||
| 7th electron orbit |
7. Plot )E versus 1/8 and determine the slope. Include the units for the slope.
Slope = __________________ % error compared to 1240 eV.nm __________
8. Set up the fiber optic cable next to the hydrogen spectrum tube and turn on the tube.
9. Open the Ocean Optics program (OOI) and measure the wavelengths for the lines you observe. Record the measured values in the above data table.
(The instructor needs to show you how to setup the equipment.) The instruction mostly for the olds computers .
10. Adjust the position of the cable-head so that the intensity of the highest peak is close to the maximum count.
11. Click "View", select "Grid" and select "Enabled". Copy the wavelengths from the table above. Record the intensity counts for all the peaks.
Intensity of the hydrogen lines:
| Wavelength of the line | Intensity count of the line |
12. Replace the hydrogen tube (Caution: Hot) with the helium tube and repeat procedure (10).
13. Record the wavelengths and intensity counts for all the peaks of the helium spectrum.
| Wavelength of the line | Intensity count of the line |