Wave & quantum behaviour Flashcards
(42 cards)
How is a standing wave made?
When 2 waves with the same wavelength travel through the same material in opposite directions
What is the difference between a node and an antinode?
Node = a place of no displacement on a standing wave
whereas antinode = a place of maximum displacement
When does constructive interference occur?
When waves are in phase and their path differences are a whole no. of wavelengths apart
When does destructive interference occur?
When waves are out of phase and their wavelengths are half a wavelength different
When does a path difference equal constructive interference? and destructive interference?
Constructive: when path dif. = a whole number of wavelengths
Destructive: when path dif. = not a whole number of wavelengths, e.g. 6.4pi
Equation for angular velocity
w = 2piF (frequency)
What is the principle of superposition?
Says that when 2+ waves overlap, the sum of the amplitudes of each wave equals the resultant displacement
What is the relation between energy/light intensity and amplitude?
Light intensity is proportional to amplitude^2
2 equations involving refractive index
n = sini / sinr n = 1 / sinC
When a wave crosses a boundary, what feature doesn’t change out of v, f, and wavelength?
Frequency doesn’t change. so v is proportional to wavelength
What is the speed of light and the speed of sound?
Speed of light = 3 x10^8 ms-1
Speed of sound = 343 ms-1
In the EM spectrum, which out of speed, wavelength and frequency is constant?
Speed is constant.
Which type of waves can be polarised and why?
Transverse, because they vibrate in multiple planes, whereas longitudinal waves vibrate in only one plane so can’t be polarised
If you have 2 polariser filters (polariser then analyser) in front of a light source, how do you change the brightness of light?
Rotate the 2ND filter, rotating the 1st won’t affect the brightness, though it does polarise the light
How can you position an analyser filter (the 2nd filter) to cut out all light from a source?
Align it at 90 degrees to the polariser
Equation relating number of fringes, wavelength and slit separation
dsinø=n lambda
How can you tell the amplitude of a wave from the number of slits?
Number of slits = amplitude
Why does 3 slits mostly not create any completely dark spots in between fringes, like 2 slits does?
-.- -.-.- =.=.=.=.= -.-.- -.-
Because 3 slits means there are 3 phasors (e.g. at 0, pi, 2pi) so as two cancel out another phasor will remain, creating 1/9 of the brightness, resulting in many places having dots of light rather than no light
Does
a) a wide slit
b) a narrow slit
create narrow or wide patterns?
a) wide slit = narrow pattern
b) narrow slit = wide pattern
How does the spacing of slits affect the spacing of fringes?
Closer together slits = further apart fringes
Further apart slits = closer together fringes
What is the fundamental frequency on a standing wave?
It’s the frequency of the longest standing wave that can be created on a string (i.e. the largest frequency). Wavelength = 2L
Why does a long, closed (at one end) tube give lower notes than an open tube?
Because it’s got a lower fundamental frequency since there would be a node at the closed end and an antinode at the open end, so it’s wavelength = 4L, whereas if it’s open with antinodes at both ends, its wavelength would = 2L.
So a closed tube has a lower frequency + longer wavelength = lower notes
How do you get a sharper interference pattern?
Diffract the light through more slits (the bright bands become brighter and narrower)
Equation for the energy carried by a quantum
E = hf
h=6.63x10^-34
