physics - waves Flashcards
what are the 2 types of waves
mechanical and electromagnetic waves
what is the definition of a mechanical waves and give examples
a mechanical wave needs a medium.
examples : waves on a guitar string , water waves , seismic waves.
what is the definition of an electromagnetic waves and give exampled
the electromagnetic wave does not need a medium.
examples : radio waves , infrared , ultraviolet.
what is the definition of a longitudinal wave ?
in a longitudinal wave the oscillations of the particles are parallel to the direction in which the wave travels.
what is the definition of a transverse wave ?
in a transverse wave the oscillations of the particles are perpendicular to the direction in which the wave travels.
give some examples of a longitudinal wave ?
sound
give some examples of a transverse waves ?
radio waves
microwaves
water waves
mexican wave
what is the definition of frequency ?
frequency is the number of waves that pass a point each second.
what is the definition of periodic time ?
the periodic time is the time taken for 1 whole oscillation.
what is the wave speed equation ?
wave speed = frequency x wavelength.
(m/s) (Hz) (m)
what is the definition of diffraction ?
diffraction is the way that waves spread out as they come through a narrow gap or go around obstacles.
when does diffraction occur ?
diffraction occurs when waves pass through gaps.
when does diffraction work best ?
diffraction works best if the wavelength of the gap is longer or narrower.
key fact about diffraction
if the gap is too large most of energy gets through , but most of waves pass straight through so diffraction is ineffective.
how can we hear around corners but not see around corners ?
light has a much smaller wavelength than the width of the doorway so there is little diffraction. the wavelength of sound is closer to the width of the doorway so there is more diffraction.
describe how a longitudinal wave travels through air ?
the particles oscillate parallel to the direction in which the wave moves, through a series of rarefactions and compressions in the air .
what is the definition of displacement ?
displacement is the distance from the equilibrium position.
what is the definition for amplitude of a wave ?
the amplitude of a wave is the height of the wave form the middle to a peak or trough.
what is constructive interference ?
constructive interference is when the crests or troughs of 2 waves coincide , they combine to create an amplified wave . the two waves are in phase with each other , there is 0 phase difference between them.
what is destructive interference ?
destructive interference is where the crests of 1 wave are aligned with the troughs of another, they cancel each other out . the waves are out of phase or interphase with each other.
what is the definition of superposition
superposition is the adding together of wave displacements that occurs when two separate sources overlap. the displacements add mathematically.
what is phase difference ?
phase difference is when 2 points which are always moving in the same direction are said to be in phase.2 points a whole wavelength apart are in phase.
what is antiphase
two points which are always moving in the opposite direction are said to be in antiphase. two points half a wavelength apart are in antiphase.
describe what is meant by
coherence
waves are coherent of they have the same frequency and wavelength and a constant phase relationship.