Experiment 11
STANDING
WAVES ON A STRING
PROCEDURE
The apparatus consists of an electrically
driven tuning fork with fixed frequency that vibrates one end of a stretched
string. The string passes over a pulley and is attached to a weight holder.
The tension of the string and hence the velocity of the wave is adjusted
by adding weights to the holder.
2. Record
the frequency, f, that is stamped on the vibrator in cell F12.
3. Measure
the complete length of the cord and its mass and enter them in cells C11:C12.
4. Attach
the cord to the vibrator-pulley assembly as indicated in Fig. 11-1.
Figure 11-1: Standing Wave Apparatus
5. Start
the vibrator by closing the switch in the electrical circuit and add just
enough weights until a standing wave pattern with at least six loops (half-wave
segments) is obtained. A standing wave pattern will be identified by a
relatively large amplitude of vibration at the antinodes.
♦♦♦ DO NOT SWITCH THE LEADS TO A DIFFERENT
POWER SUPPLY OR YOU MIGHT DAMAGE THE EQUIPMENT! ♦♦♦
By measuring the distance (L)
between the first and last nodes and dividing by the number of loops (N),
you can calculate the length of a loop and, consequently, the half-wavelength
and the wavelength, λ.
6. Record
the mass that is suspended (don’t forget the mass of the holder) in cell
A18 of the Data Table on the Worksheet.
7. Determine
the corresponding tension force and enter the value in cell B18.
8. Record
the total distance between the first and the last nodes L , in cell
C18.
9.
Continue to add weights until one less loop is produced and repeat the
measurements of suspended mass and distance between first and last nodes.
Record these values in cells A19:C19.
10.
Repeat until only three loops are produced, filling out the Data Table
cells A20:C21.
11. Print
out the Worksheet and use it to complete your lab report.