12.1 - 12.6 Flashcards
what’s the principle of superposition of waves
when two waves meet at a point the resultant displacement equals the sum of the individual displacements
what is constructive interference
superposition of two waves in phase. the resultant wave has a greater amplitude than the individual waves
what is destructive interference
superposition of two waves in antiphase. the resultant wave has a smaller amplitude than the original waves
define coherence
two waves/wave source that are coherent have a constant phase difference
define ‘path difference’
the difference in the distance travelled by two waves from the source to a specific point
whats the path difference for constructive and destructive interference
constructive: xλ
destructive: xλ+ (1/2)λ
where x is an integer
how does Young’s double-slit experiment work?
he used one source of monochromatic light. by directing it through a single slit the light diffracted and arrived at the double slit in phase. it then diffracts again at the double slit. each slit acts as a coherent source. this causes an interference pattern.
what does Young’s double-slit experiment prove?
it demonstrates the wave nature of light
what is a stationary wave
when two waves of the same frequency travel in opposite directions and are superimposed. there is no transfer of energy
whats a node
a point on a stationary wave where there is destructive interference. the displacement is always 0
whats an antinode
a point on a stationary wave where there is constructive interference. the displacement is the greatest (at the amplitude)
what’s the distance between adjacent nodes or antinodes
half the wavelength of the stationary wave
how is phase difference different along a stationary wave?
between adjacent nodes, the phase difference is always 0 because each point reaches its maximum positive displacement at the same time.
on the other side of the nodes, the points are in antiphase. as one reaches its maximum positive displacement the other reaches its maximum negative
how are stationary waves on a string formed
when plucked a progressive wave travels along the string. It reflects off each end creating two progressive waves traveling in opposite directions forming a stationary wave
what is the fundamental frequency
the minimum frequency of a stationary wave.
whats the fundamental frequency of a string
when the wavelength is twice the length of the string
what is a harmonic
an integer multiple of the fundamental frequency. these are the frequencies that can form stationary waves
how are stationary waves different in a tube open at one end and closed at the other
a node must be at the closed end but an antinode must be at the open end for a stationary wave to form. the fundamental frequency is 1/4 λ
how are harmonics different in a tube open at one end and closed at the other
they are not integer multiples of the fundamental frequency. they are odd number multiples. this is because there must be a node at one end and an antinode at the other.
