Tuesday 24 Nov:

Must know this formula (but it is not on the sheet):                

****       Vstring = √ {(FTension) / (mass/Length)}    

 

 Journal:

1. The number of segments in the standing wave shown in the diagram above is ____

2. The number of nodes & antinodes in the standing wave shown in the diagram above is ____.

3. A standing wave is formed when ____.

a. a wave refracts due to changes in the properties of the medium.

b. a wave reflects off a canyon wall and is heard shortly after it is formed.

c. red, orange, and yellow wavelengths bend around suspended atmospheric particles.

d. two identical waves moving different directions along the same medium interfere (constructive & destructive).

 

 

 

 

 

 

 

 

 

Answer:

1. 8 segments

2. (8 nodes)(7 antinodes)

3. D

 

 

                             

 

 

 

 

 

 

 

 

 

 

1. Explain the number and location of antinodes & nodes of the fundamental freq (stand wave) in two resonating pipes (2.0 m), and the l’s of each to that of a string:

  • a. One is open at both ends
  • b. one is open at one end and closed at the other
  • c. string

 

 

 

 

  

 

            a. Open ended: It has two antinodes (always at open ends) and one node (in the middle). This means that the standing wave  is taking up ½ of the pipe (l = 2L).

                l = twice the length of the pipe or 4.0 m

                        frequency:  f1 = V/2L

 

            b. One end closed: It has one antinod (open end) and one node (closed end). This means that the standing wave is taking up 1/4 of the pipe (l = 4L).  l = four times the length of the pipe or 8.0 m

               frequency: f1 = V/4L

 

    c. String has two nodes (always at ends) and one antinode (in the middle). This means that the standing wave is taking up ½ of the string. (l = 2L).

                l = twice the length of the string or 4.0 m

                        frequency:  f1 = V/2L

    (String's  l is same as the open ended, but has 2 nodes)

 

 

 

 

2. Compare the intensity, frequency, amplitude, wavelength, velocity and pitch of a point source at a distance 3d and d from the source?

 

 

 

 

 

 

 

  •  Intensity decreases (live all radiation & fields of force) 1/r2 or 1/32 = 1/9th as much

  • Frequency of sound doesn’t change due to distance

  • Amplitude is intensity:  so is 1/9th as much

  •  l doesn’t change

  •  Velocity doesn’t change because of distance

  •  Pitch is frequency: so doesn’t change

 

 

 

3. Compare the frequency, velocity, l standing wave on a string to the sound wave generated by the string.

     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • Same Frequency, the string pushes the air (compression waves) at the same frequency of its vibration.

  • Velocity on a string is different (almost always) than the velocity in air (which is normally about 343 m/s). V on a string depends on mass per meter, tension, length, etc.