Frequencies of the normal mode in standing waves in a string fixed

In summary, sound waves are created by pressure variation in the air. The waves created due to displacement of air (like when you whistle) are different because they are also affected by the air's temperature.
  • #1
noobie!
58
0
hi,im a newbie over here,my physics quite poor so i really need help by understanding it,i jz wanted to ask could any1 please explain to me what is in phase,&out of phase?;im totally baffled.:blushingAnd what's frequencies of the normal mode in standing waves in a string fixed in both ends?i hope any1 cud help me with this..tq!:blushing:
 
Physics news on Phys.org
  • #2
If you have two waves, let's assume of the same frequency, you can 'define' a phase difference between them. The phase difference simply tells you how much one wave is 'ahead of' the other wave, and is often given in degrees (0 to 360) or radians (0 to 2pi).

If you look at the following image:
phase.jpg

Clearly, the waves have the same frequency, but one wave is slightly ahead of the other: there is a phase difference between the two.In general, there are a few phase differences of special interest: a phase difference of 0 radians (or 0 degrees) means the waves are exactly "in phase", one is not ahead of the other. A phase difference of pi (or 180 degrees) is often called exactly "out of phase", one wave is exactly half a wavelength ahead of the other wave, which means that the peaks of one wave fall together with the troughs ('dips') of the other wave.

When the two waves are for example sound waves (it is equally valid for all other kind of waves) and when they exist in the same place, then the waves will interfere. A phase difference of 0 will then cause the interference wave to be the sum of both waves. With a phase difference of pi (180 degrees), the peaks and troughs will cancel each other out and the resulting wave is zero everywhere: there is no longer a wave.
 
  • #3
THANKS a lot man..now i can really understand it completely,thx for ur help,one more thg I am nt clear abt it was the standing waves in an open end due to displacement of air and pressure variation in the air!?i wud appreciate it very much if i understand it...tq!:smile:
 
  • #4
I assume you are talking about sound waves in an open ended tube? Then yes, they are caused by pressure variation in the air; as are all sound waves...
 
  • #5
oh you sound waves..but what i dun really understand is the pattern of the waves..why does the waves due to displacement of air differ frm pressure variation in the air?
 

1. What is a normal mode in standing waves?

A normal mode in standing waves refers to the specific pattern of oscillation that a string fixed at both ends produces when it vibrates. It is characterized by nodes (points of no displacement) and antinodes (points of maximum displacement).

2. How do you determine the frequency of the normal mode in standing waves?

The frequency of the normal mode in standing waves can be determined by the formula f = (n/2L) * sqrt(T/μ), where n is the number of nodes, L is the length of the string, T is the tension in the string, and μ is the mass per unit length of the string.

3. How does changing the length of the string affect the frequency of the normal mode?

Changing the length of the string will change the frequency of the normal mode. As the length increases, the frequency decreases, and vice versa. This is because the wavelength of the standing wave is directly proportional to the length of the string, and frequency is inversely proportional to wavelength.

4. Can the frequency of the normal mode be altered by changing the tension in the string?

Yes, the frequency of the normal mode can be altered by changing the tension in the string. Increasing the tension will increase the frequency, while decreasing the tension will decrease the frequency. This is because tension affects the speed of the wave, which in turn affects the frequency.

5. What factors affect the frequencies of the normal modes in standing waves?

The frequencies of the normal modes in standing waves are affected by the length, tension, and mass per unit length of the string. Additionally, the number of nodes and the speed of the wave also play a role in determining the frequency of the normal mode.

Similar threads

A Real image of a sawtooth standing wave in a musical string?
    • Other Physics Topics
2
Replies
41
Views
14K
Understanding Normal Modes and Standing Waves in Vibrating Systems
    • Other Physics Topics
Replies
1
Views
1K
Length of string in a standing wave
    • Introductory Physics Homework Help
Replies
19
Views
300
I How can phonons "travel" if they are excitations of normal modes?
    • Atomic and Condensed Matter
Replies
7
Views
3K
Understanding the Fundamental Frequency f1 and Its Role in Sound Waves
    • Other Physics Topics
Replies
6
Views
1K
How can standing waves be created on a string fixed at both?
    • Other Physics Topics
Replies
2
Views
992
B Is this an accurate description of standing waves?
    • Other Physics Topics
Replies
6
Views
1K
I Atom as a harmonic oscillator of radition
    • Other Physics Topics
Replies
14
Views
2K
I Error tolerant normal mode frequency
    • Classical Physics
Replies
7
Views
1K
B Moving to a higher harmonic in a standing wave
    • Other Physics Topics
2
Replies
40
Views
4K

Hot Threads

Recent Insights

Back
Top