Waves Flashcards
What is a wave?
Propagation of oscillation in a medium
What are the types of waves?
Mechanical, electromagnetic and matter waves
What type of wave requires a compressible medium?
Mechanical waves
Wavelength
Distance between two points of a wave that have the same phase.
Frequency is an internal property. What does that mean?
It remains constant when the wave passes from one medium to another.
Velocity of propagation and wavelength depends on..
Properties of the medium
Transverse wave
Direction of oscillation is perpendicular to the direction of propagation. Example: surface waves in water, electromagnetic waves (light)
Longitudinal wave
Direction of propagation is parallel to the direction of oscillation. Example: sound waves in air.
Linear polarization
A wave is linearly polarized if one distinct direction of oscillation is selected.
In a linearly polarized wave the plane of oscillation and the direction of propagation remains..
Constant with time
Wavefront
A surface containing points of waves in identical phases.
Spherical wave
Waves originating from a common point, but propagating in every direction in space (spatial waves).
Examples: clapping your hand or surface waves when tossing a pebble in a pond.
Plane wave
A wave in which the wavefronts form planes that are parallel to each other but perpendicular to the direction of propagation. Example: light beam of a laser pointer
Reflection
Incident wave (or part of it) turning back at the interface between different media.
Law of reflection: a=b
What determines the color of an object?
The reflection of light
How does ultrasound work?
Reflection of ultrasound at the boundary of two different organs or tissues.
Refraction
The change in direction of propagation of a wave when passing through an interface between two media.
The law of refraction (in case of light - Snell’s law)
The relationship between angles before and after the interface
Interference
Occurs when two (or more) waves meet. The requirements for interference is that the waves have identical wavelengths and their phase difference stays constant in time.
Constructive interference
When two waves meet in identical phases the resultant wave will become larger.
Equal amplitudes and identical phases gives amplitude with twice the size.
Destructive interference
When two waves superpose in precisely opposite phases, the resultant waves will become smaller.
If the two waves had equal amplitude and opposite phases, the amplitude would be zero.
Standing wave
Resultant pattern of interference between plane waves that propagate agains each other and have identical wavelengths and amplitudes.
Example: incident and reflected waves interfere.
Each point of a standing wave oscillate with different amplitudes.
Amplitude of the nodes of standing waves
Zero
Amplitude of the anti-nodes
Maximum
Distance between two nodes
Half the wavelength
Diffraction
Change in the direction of wave propagation due to an obstacle or slit in the path of the wave (not interference).
The smaller the size of the obstacle or slit, the greater the effect of diffraction will be.
Huygens-fresnel principle
A concept of wave propagation. Every point on a wavefront acts as a source of new elementary waves. Can be imagined as spherical waves propagating in every direction in space.
Sound
Mechanical vibration that propagates as a wave in compressible materials.
Audible sound
20-20 000 hz
Sound propagates as what kind of wave in solid materials?
Transverse and longitudinal
What kind of wave does sound travel as in liquids and gases?
Longitudinal waves
The frequency determines what in audible sound?
The pitch
The amplitude determines what in audible sound?
The loudness
The collection of fundamental and higher harmonics determine the
Timbre
The compressibility of a material is important to what kind of wave?
Speed of sound
The easier it is to compress a material (greater compressibility), the farther are its component molecules from each other and it will take longer for the molecules to pass on the vibrations.
Sound propagates slowly in great compressible materials
Mechanical waves propagates as transverse waves only in … materials
Solid.
