Waves Flashcards
define waves
It is the disturbances that carry energy and momentum from one point to another point in space without the actual flow/transfer of the medium.
whata re the types of waves bsed on medium of propogation
i) Mechanical waves: These are waves that require a medium for propogation. Eg: sound waves, seismic waves, water waves.
ii) Non mechanical waveS: These waves do not require a meidum to propogate. Eg: EM waves( light, IR, UV X rays)
iii) Matter waves: They are associated with constituents of
matter : electrons, protons, neutrons, atoms and
molecules. They arise in quantum mechanical
description of nature
differentiate between transverse and longitudinal waves
Transverse waves:
- direction of vibration of particles is perpendicular to the direction of propogation of the wave( individual particles execute simple harmonic motion about mean position in direction perpendicular oto direction kf propagation of wave.)
- Distubrances are transferred in the form of crests, troughs.
- It is possible only in elastic media ( solid)
Longitudinal waves:
- direction of vibration of particles is parallel to the direction of proporgation of wave
- Disturbances are transferred in the form of compressions and rarefactions.
- It is possible in all media( solid, liquid, gas)
what dpes the speed of a wave in a medium depend upon
i) elastic properties of the medium
ii) inertial properties of the medium
what are progressive waves
A wave, transverse or longitudinal, is said to be progressive if it proporgates from one point in the medium to another with constant amplitude and without change in its energy.
what is reflection of waves
when a pulse is travelling from left to right reaches a rigid wall, it gets reflected. The reflected pulse passes through the same medium. Thus the speed, frequency, wavelength of reflected pulse will be the same as the incident, but it will undergo a phase reversa;/
what is the principle of superposition of waves
When 2 waves passing through the same medium overlap, the total displacement is given by the algebraic sum of the individual displacements, caused by each wave.
what will happen if a wave hits a non rigid barrier
If on the other hend, the boundary point is
not rigid but completely free to move (such as in
the case of a string tied to a freely moving ring
on a rod), the reflected pulse has the same phase
and amplitude (assuming no energy dissipation)
as the incident pulse. The net maximum
displacement at the boundary is then twice the
amplitude of each pulse. An example of non- rigid
boundary is the open end of an organ pipe.
what are stnding waves
When the wave hits the rigid boundary it bounces back to the original medium and can interfere with the original waves. A pattern is formed, which are known as standing waves or stationary waves.
Whenever two waves with almost similar frequencies, wavelength, and amplitude traveling throughout opposing orientations collide, a standing wave is formed.
what are the charactertistics of stationary waves
- the distrubances are confined to a region between the starting and the reflecting point
- the waves are not progressive i any driection
- the total energy of the wave is twice the energy of each incident wave and reflected wave.there is no net transfer of energy from one point to another point in the medium
-there are certain particles in the medium who are permenenaently at rest. these are called nodes - there are certain particles who have the maximum amplitude and are called as antinodes.
- In a standing wave, the medium is split into a number of segement and each segment is vibrating up and down as a whole
- all the particles in oen segment are in the same phase.
what are normal modes
The system cannot
oscillate with any arbitrary frequency (contrast
this with a harmonic travelling wave), but is
characterized by a set of natural frequencies or
normal modes of oscillation.
what is fundamental mode
The lowest possible natural frequency of a
system is called its fundamental mode or the
first harmonic.
what are beats
When 2 sound producing bodies of nearly same frequencies and same amplitudr are sounded together, the resultant sound comprises of alternate maxima and minima. This phenomena of aleternate variation in intensity of sound w/ time is called beats.
what is beat frequency
the number of beats hear per second is called beat frequency
for the formation of distinct beats, the beat frequency must not be more than 10Hz
How does energy transfer take place in mechanical waves
In mechanical waves energy transfer takes place due to coupling through elastic forces between neibhoruing oscillating particles of the medium
