Wave Flashcards
What is a wave?
Propagation of oscillation in a mediuum.
What kind of wave is sound?
Mechanical wave.
What is a wavelength and what is the base unit?
The distance between two points that are in the same phase (m).
What is velocity of propagation?
Velocity: distance covered by one period (T) : c = lambda/T = Lambda * 1/T = lambda * frequency
Is frequency constant or does it change?
It is constant.
What does the velocity of propagation and wavelength depend on?
The properties of the medium, as the frequency is constant.
It is true for all kinds of waves.
Give an example of a transverse wave. Can it be polarized?
Electromagnetic waves (light). Yes, as it is a transverse wave.
Give an example of a longitudinal wave.
Sound.
What is refraction?
The change in the direction of propagation, when passing through an interface between two media.
The relationship between the angles before and after the interface (incident angle and angle of refraction).
What is interference?
What is the requirement?
When two or more waves meet.
The requirement is that the waves have identical wavelengths and their phase diffeerence stays constant in time.
What is a standing wave?
What is the formula?
What happens if the length is shorter?
The pattern of intereference between plane waves that propagate against each other and have identical wavelengths and amplitudes.
The distance between the two notdes equals half the length.
L= k * lambda/2. (K =1,2,3). If the length is shorter, the lambda will be shorter as well and the frequency increases as the velocity of propagation is constant.
Why does pitch of sound increase if we make it the guitar string shorter?
If the length is shorter, then the wavelength will be shorter as well. Thus the frequency (which determines the pitch) increases because the product of wavelength and frequency is constant.
What is diffraction?
The change in the direction of wave propagating due to an obstacle or slit in the path of the wave (not an interface!)
The smaller the size of the obstacle/slit, the greater the effect of diffraction will be.
What is the Huygens-Fresnel principle?
Concept of wave propagation. According ot this model, every point on a wavefront acts as a source fo new elementary waves.
What is sound?
What is the range of audible sound?
A sound is a mechanical vibration that propagates as a wave in compressible materials.
Audible sound: 20-20 000 Hz.
Is sound a transverse or longitudinal wave?
Both transverse and longitudinal in solid materials, but ONLY as longituninal in liquids and gases, as there are no shearing forces acting at rest.
What does the speed of sound depend on?
Depends on the compressibility of the material. If it is not as compressed (e.g. a sponge); it has a high compressibility - sound propagates slowly.
Low compressibility; e.g. concrete wall - sound propagates quickly.
Which statement is true?
A: In case of longitudinal waves the direction of oscillation and propagation are perpendicular to each other.
B: Mechanical waves can only by transverse.
C: Mechanical waves propagate as transverse waves onlyin solid materials (and partially on liquid materials)
D: Waves always carry material.
C.
What is true about speed of light in transparent materials?
The speed of light is smaller.
What happens to the wavelength when a wave slows down in the medium?
The wavelength becomes shorter, but the frequency remains constant.
What is true about linearly polarized waves?
The plane of oscillation and direction of propagation remains constant with time.
Give an example of a plane wave.
A laser pointer.
What is total diffraction?
If the slit is so small - only one spherical wave will originate from this point, and as there are no other elementary waves to inferfere with, this will be the new wavefront.
The wave will propagate in every direction behind the slit, thus the diffraction is total.
What is pitch of audible sound determined by?
What is loudness determined by?
Pitch is determined by frequency.
Loudness is determined by amplitude.
What is the role of frequency in speed of sound?
Speed of sound is independent of frequency - so every sound propagates with the same speed in the medium.
What is the range for ultrasound?
20 kHz to 1 MHz (10 9)
What is the range for hypersound?
Above MHz (above 10 9)
