11.1 - 11.9 Flashcards
Waves
define progressive wave
a wave that transfers energy, but not matter, through a medium
define Transverse wave
a wave in which the particles in the medium oscillate perpendicular to the direction of energy transfer
define longitudinal wave
a wave in which the particles in the medium oscillate parallel to the direction of energy transfer
examples of transverse waves
EM waves,
S- waves
examples of longitudinal waves
sound waves,
P- waves
what’s the range of human hearing
20 - 20k Hz
define displacement
distance from the equilibrium position in a particular direction
define amplitude
maximum displacement from the equilibrium position
define wavelength
the minimum distance between two points oscillating in phase
define wave period
the time taken for a wave to complete one oscillation
define frequency
the number of wavelengths that can pass a single point per unit time
define wave speed
the distance travelled per unit time
define phase difference
the difference between the displacements of particles along a wave or on different waves. measured in degrees or radians
define the term ‘antiphase’
when particles along a wave have a phase difference of 180 degrees
why are longitudinal waves faster in a solid?
the particles are closer together so the transfer of energy is faster.
define reflection
when a wave changes direction at the boundary between two different media and remains in the original medium
what is the law of reflection
the angle of incidence equals the angle of reflection
what is the angle of incidence/reflection
the angle between the normal and the ray of incidence/reflection
define refraction
when a wave changes speed and direction as it passes from one medium to another
what does refraction change about a wave
the speed and wavelength. it can not change the frequency
define diffraction
when waves pass through a gap or around an object they spread out. The speed, wavelength and frequency of diffracted waves remain the same.
what affects diffraction
the size of the wavelength compared to the size of the gap. if they are similar then diffraction is most significant.
define polarisation
when the oscillations of a transverse wave are limited to one plane
what is a plane polarised wave
a transverse wave which has its oscillations limited to a single plane
why can’t longitudinal waves be polarised
their oscillations happen parallel to the direction of energy transfer which means they are already limited to one plane
define ‘partially polarised’
when there are more oscillations in one particular plane but the wave is not completely polarised
define wave intensity
the power passing through a surface per unit area
how are wave intensity and distance from the source linked
intensity is inversely proportional to the distance from the source^2
how are wave intensity and amplitude linked
intensity is directly proportional to the amplitude^2
which end of the EM spectrum has the highest frequency
Gamma
why can gamma rays and X-rays have the same wavelength
the type of wave is not determined by the wavelength. it’s determined by the source.
whats the wavelength range of each type of EM Wave in meters
Gamma- >10^-16 X-ray- 10^-8 to 10^-13 UV- 4*10^-7 to 10^-8 VL- 400-700nm IR- 7*10^-7 to 10^-3 Microwave- 10^-3 to 0.1 Radiowave- <10^6
what is a use of polarised waves?
communication transmitters. a horizontally and a vertically polarised wave will have minimal interference with each other
what is a refractive index
the ratio of the speed of light in a material to the speed of light in a vacuum
define total internal reflection
the reflection of all light hitting the boundary between two media, back into the original medium. the original medium must have a higher refractive index and the angle of reflection must be greater than the critical angle
define critical angle
the angle of incidence between two media that will cause an angle of refraction to be 90 degrees.
