Quanta and waves Flashcards
Evidence of quantum theory
black body radiation curves
the UV carastrophe
experimental evidence for wave-particle duality
-the photoelectric effect (light behaving as particles)
-electron diffraction patterns (particles behaving as waves)
formula for particles moving at non-right angles to field
F=qBvsinx
What happens if a particle is moving parallel to a field
It will not be deflected
What does F=qvB equal
Fc=mv^2/r
as the force exerted is a centripetal force
SHM graphs for s, v, a against t
For a spring that has been raised
s: starts at 1
v: starts at 0 and goes down
a: starts at -1
F=-ky graph
negative gradient meeting (0,0)
What does the angular frequency and period of oscillation (SHM) not depend on?
the displacement of the object from equilibrium
SHM: When are velocity and acceleration at a maximum and when are they 0?
velocity:
maximum when y=0
0 when y=A or -A
acceleration:
maximum when y=A or -A
0 when y=0
When is Ek and when is Ep at their maximum?
What does Etotal equal?
Ek: y=0
Ep: y=A or -A (Ek=0)
Etotal=Ep+Ek
Nodes-points and anti-nodes-points
Nodes-points: Minimum (0) disturbance on a stationary wave
Anti-nodes-points: Maximum disturbance on a stationary wave
Where will standing waves form? And what do these frequencies depend on?
At particular frequencies known as resonant frequencies.
They depend on many factors-length of tube, tension in string, volume of air
First resonant frequency=first harmonic/fundamental frequency
What do we need for constructive and destructive interference
coherent sources-sources of waves with a constant phase relationship
2 types of interference
Interference by division of wavefront: e.g. double slit or grating
Interference by division of amplitude: uses optical path difference
What is interference by division of amplitude?
-splitting the ray into two via reflection and refraction
-The amplitude of the ‘split’ beams is less than the original
What phase change does a wave reflecting off a material with a higher refractive index undergo?
pi
This gives the appearance of the wave ‘flipping’ and adds a half wavelength to the opl
What phase change does a wave reflecting off a material with a lower refractive index undergo?
no phase change
coated/bloomed lenses
-division of amplitude
-can be made non-reflective for a specific wavelength of light
-e.g.cameras, glasses
-d=lamda/4n
-increasing n
Thin film interference
-A complex pattern of coloured fringes are produced due to interference by division of amplitude
-Different colours are produced depending on a number of factors:the angle the film is viewed, the thickness of the film, the opd between both rays as they
-e.g.puddle
-decrease in n
wedge fringes
🔺x=(lamdaxl)/2d
l=length of bottom of wedge
d=thickness of wedge gap
-the thickness of the air in the derdge is increasing left to right so the opd between the reflected rays is increasing
-a birght fringe is deen whrn the opd leads to constructive interference, and a dark fringe occurs ehrre destructive interference is taking place
-a thinner wedge makes the fringe more spaced out
What type of wave can all EM waves be categorised as?
transverse waves
They consist of electric and magnetic fields at right angles to the direction of travel and each other
How do you polarise an EM wave?
-passing it through a polarising filter
-only waves that have their electric field vector aligned with the transmission axis of the filter will pass through
Rotating the analyser will gradually reduce the amount if light transmitted
-at 90 degrees, the light is blocked
polarisation by reflection
Polarisation can also be caused by the reflection of light from the surface of an electrically insulating material
The degree of polarisation changes with the angle of incidence
Brewster’s angle
ip
unpolarised light reflecting off a surface can be plane polarised (parallel to the surface) if the angle of incidence is equal to brewster’s angle
The brewster’s angle is found only when the reflected ray and refracted ray are at right angles to each othrr
Applications it polarisation
-polarising filters in sunglasses/camera lenses
-cinema 3D glasses
-Birefringence
What is a method of damping?
placing mass in a more viscous medium
increase surface area of mass
In 3D glasses, how are two polarising filters arranged so that the 2 images on the screen do not interfere
90 degrees to each other
how do glasses with 2 polarising filters, 1 for each eye, enable a different image to be seen by each eye?
The filter for each eye allows light from 1 projected image to pass through while blocking the light from the other projector
Considering its De Broglie wavelength, why might an electron be considered a wave?
Its wavelength is comparable to its atomic radius so it is suitable for demonstrating interference
Explain why a particular thickness of (zinc oxide) coating is non-reflective for particular wavelengths of light.
A particular thickness will produce destructive interference of the reflected rays for a particular wavelength of light
When viewed under white light, the (zinc oxide) coating appears blue-green in colour. Why?
-The coating is anti-reflecting for red light/red light is transmitted
-blue and green light is reflected
