Mechanics 4 Flashcards
What are the conditions for the medium for a mechanical wave to propagate through it?
Should be elastic
Resistance of medium should be small
Define a mechanical wave
A mechanical wave can be considered as and oscillatory disturbance traveling through a medium without change in form.
Define transverse waves
The waves in which the particles of medium vibrate in a direction perpendicular to the direction of propagation of waves are called transverse waves.
Define longitudinal waves
The waves in which the particles of the medium vibrate in a direction parallel to the direction of propagation of waves are called longitudinal waves,
Define amplitude of a wave
The maximum displacement of any particle from thE mean position is called the amplitude of the wave.
Define Period of a wave
The time taken by any particle to complete one vibration is known as the period of the wave.
Define frequency of a wave
The number of vibrations per second by a particle is called the frequency of the wave.
Define wavelength of a wave
The distance between two consecutive particles of the medium which are in the same phase or differ in phase by 2pi radians is called wavelength of the wave.
Define velocity of the wave
The distance travelled by the wave in one second is called the velocity of the wave.
Explain double periodicity of a wave
Form of wave repeats itself in equal intervals of time- periodic in time
Form of wave repeats itself at equal distances- periodic in space
Defined progressive waves
Progressive waves are waves which continuously travel in a given direction
How much phase difference does a path difference of x correspond to?
2π*x/λ
Give the expression for representing a one dimensional simple harmonic progressive wave traveling in the direction of the positive x-axis.
y= asin[ω(t-(x/v))]
Or
y= asin[2π((t/T)-(x/λ))]
Give the expression for representing a one dimensional simple harmonic progressive wave traveling in the direction of the negative x-axis
y= asin[ω(t+(x/v))]
Or
y= asin[2π((t/T)+(x/λ))]
Why is a small surface sufficient for reflection of light waves whereas a large surface required for reflection so found waves?
Wavelength of light waves- angstrom
Wavelength of light waves- mm
What happens when a transverse wave is reflected from a fixed surface?
Crest becomes trough
Trough becomes crest
What happens when a transverse wave is reflected from a free surface? (Rarer medium)
Crest remains crest
Trough remains trough
What happens when a longitudinal wave is reflected from a fixed end? (Denser medium)
Compression remains compression
Rarefaction remains rarefaction
What happens when a longitudinal wave is reflected from a eared medium?
Compression reflected back as rarefaction
Rarefaction becomes compression
What is change of phase of a wave incident on the boundary of a denser medium?
Phase changes by π radian
State the principle of superposition of waves
The principle of superposition of waves states that when two or more waves traveling through a medium arrive at a point of the medium simultaneously, each wave produces its own displacement at the t point independently of the others. Hence the resultant displacement at that point is equal to the vector sum of the displacement due to all the waves.
Define constructive interference
If two transverse waves superimpose in phase then a crest due to one coincides with a crest due to other or a trough due to one coincides with a though due to the other, then the resultant amplitude at that point is maximum and is called constructive interference.
Define destructive interference
If a crest due to one waves coincides with a trough due to the other, or vice versa, the resultant amplitude due to interference is minimum and is called destructive interference.
explain Quincke’s Tube experiment
nλ= constructive (n+(1/2))λ= destructive