final Flashcards
1
Q
true or false, each point of a wave front acts like a new point source
A
true
2
Q
how do we see patterns of light during young’s double slit experiment?
A
because the wave point sources diffract around the slits, which allows them to interact with each other and form patterns on the slits
3
Q
what is coherent light?
A
synchronous
4
Q
what is monochromatic light?
A
has 1 frequency
5
Q
do we count bright or dark spots for double slit experiment?
A
bright and dark (we have a formula fo contructive and destructive)
6
Q
what are the wavelengths of visible light?
A
380-700 nm
7
Q
what is the division of the electromagnetic spectrum?
A
8
Q
how are the m values organized on the double slit experiment?
A
9
Q
what happens when a wave is reflected off of a higher n medium?
A
phase shifted by pi
10
Q
is a higher n a faster or a slower medium?
A
slower medium
11
Q
when light goes through a thin film, what type of rays result?
A
reflected and refracted rays
12
Q
what are the two reasons for phase difference in thin films?
A
path difference and phase shift pi
13
Q
are reflected and incident rays actually angled in thin films?
A
no, we just draw them like that
14
Q
in a thin film, which parameters change?
A
lambda and vwave
15
Q
what’s interference?
A
wave combines/cancels out
16
Q
for a single slit, what happens in the case where lambda is much bigger than the aperture of the slit?
A
its constructive everywhere (big bright spot)
17
Q
for a single slit, what happens in the case where lambda is much smaller than the aperture of the slit?
A
almost no diffraction, one bright spot the size and shape of the slit is made
18
Q
what is the perfect case for lambda for the single slit experience?
A
lambda is smaller than a, but not much smaller
19
Q
what does the single slit intensity m value distribution look like?
A
20
Q
why does lambda need to have a certain length relative to aperture in the single slit experiment?
A
21
Q
does the single slit formula measure bright or dark spots?
A
dark, but it has the bright spot formula for double slit (except no m=0)
22
Q
what improves resolution?
A
making teta min smaller
23
Q
what si the Raleigh criteria for resolution?
A
we can distinguish 2 features of an image when the central max of one lands on the first min of the other
24
Q
what is the formula for teta min when we have a rectangular slit?
A
teta min= lamda/aperture
25
is it better for resolution to have a big or a small diameter?
big
26
is it better for resolution to have a big or a small lambda?
small
27
does zooming in make resolution better?
no
28
what is the real life formula we use fo resolution?
teta min= 1.22 lambda/D
29
is teta min in radians or in degrees
radians
30
what is teta min?
angle of resolution required to distinguish 2 pixels
31
why does the single and double slit effect combine in real life? what does this look like?
each single slit has diffraction of its own. it looks like the single slit shape with little double slit bright spots inside
32
what is the explanation behind the way that diffraction grating looks? how do they look?
-the spot right next to the bright spot is dark, so my dark spots are narrow. they're also brighter cause they have hundreds of rays that add up
-bright spots are located at same place as double slits, but brighter, smaller and narrower
33
what is aether?
supposed invisible medium that carries light waves
34
what is the result of the Michelson Murray experiment? what was the point of the experiment?
the speed of the earth is 0 (impossible)
-was trying to measure velocity of earth vs aether
35
what is Einstein's interpretation to the Michelson Murray experiment?
aether doesn't exist, only relative velocities exist. U CANNOT BE STATIONARY IN RESPECT TO THE UNIVERSE
36
what is the medium to light?
light has no medium
37
does an observer moving change the vwave of a light wave?
no, never
38
does an observer moving change the vwave of a sound wave?
yes
39
does the observer or the source moving change vwave?
the observer
40
what are the 2 postulates of relativity?
-the laws of physics are the same in all inertial reference frames
-the speed of light is constant in all inertial reference frames
41
what is an inertial reference frame?
traveling in a straight line at constant speed
42
in a relativity situation, what is the only thing that the 2 observers agree on?
v relative
43
who measures proper time?
the person that sees the event from start to finish at the same place ( if u can point at the beginning and its at the same place at the end, you are measuring proper time)
44
what is proper length?
length of an object (or distance between objects) from the perspective of an observer that sees the object as stationary (relative speed is 0)
45
in what dimension does length contraction occur in?
the dimension of the relative velocity
46
what are the classical wave theory predictions for the photoelectric effect?
-kinetic energy of electrons depends on intensity of life
-for a fixed intensity, kinetic energy of electrons is independent of frequency
-if no electrons are ejected, we can bring intensity of light up and some will be ejected
47
what are the actual observations for the photoelectric effect?
-kinetic energy of electrons is independent of intensity of light
-kinetic energy of electrons linearly dependent on frequency
-below cut off frequency, no electrons ejected regardless of intensity of light
-if we increase intensity, more electrons ejected (but their kinetic energy does not change)
48
what happens when we increase the intensity of light?
we increase the number of photons, but not the energy contained inside them
49
what happens when we increase the frequency of light?
we increase the amount of energy in each photon
50
what is Einstein's interpretation of light?
based off of two things:
-each light particle carries its own energy (photoelectric effect)
-light can interfere (double slit experiment)
the compromise to this was photons, which are wave packets that carry their own energy
51
what is stopping voltage?
Stopping potential is the minimum negative voltage applied to the anode to stop the photocurrent. The maximum kinetic energy of the electrons equals the stopping voltage, when measured in electron volt. this is because if u remove all kinetic energy, the electrons wont move anymore, therefore no current will be generated
52
what is de Broglie"s hypothesis?
all matter is both particle and wave, so we can through it at a double slit and get an interference pattern
53
what is a de Broglie wavelength?
if all matter is both particle and wave, they must have a wavelength: Planck/momentum
54
how does an electron intensity pattern form?
each electron lands at one slot on screen but following a probability distribution that follows our interference pattern
55
what is the Bohr atom model?
electrons are standing waves around the nucleus
56
what are the conditions for standing waves?
they need to be closed on themselves. closed boundary condition
57
why is the Bohr atom quantized?
since only certain orbits are allowed for the standing wave (electrons)
58
why are only certain/specific energies are emitted from electrons?
because they can only travel to specific n values, and if they dont absorb that exact energy level, they wont go up any values
59
what is ionization?
u can give any amount of energy cause its not quantized anymore. electron leaves quantum levels
60
what happens when a photon doesn't have a specific energy level to make electron go up?
the photon is reflected
61
what happens if I give more energy than the n=1 level?
electron is ionized
62
what are the three types of nuclear decay?
-alpha
-beta
-gamma
63
what happens during beta decay?
During beta decay, the proton in the nucleus is transformed into a neutron and vice versa. If a proton is converted to a neutron, it is known as β+ decay. Similarly, if a neutron is converted to a proton, it is known as β– decay
beta+: proton in nucleus becomes neutron, so atomic number goes down by now (but nucleon number stays the same (mass number))
beta- : gain proton in nucleus, so emits electron to balance out the charge
64
what happens during alpha decay?
decaying into a helium atom and a leftover. the mass number of the leftover is minus 4 and the atomic number is minus 2
65
what happens during gamma decay?
during decay, an electron rises to upper energy levels, and after decay it releases it as a photon. atomic number and mass number stay the same
66
what is the ratio of NC14/NC12?
1.3 x 10^-12
67
does carbon 12 decay? does carbon 14 decay?
carbon 12: no
carbon 14: yes
68
when the mass on one side of a reaction doesn't equal to the mass on the other side of the equation, what happened to the mass?
it got converted into energy (use formula E=mc^2
69
what are the two formulas for beta decay at the particle level?
-neutron= proton+ electron+ neutrino
-proton= positron+ neutrino+ neutron
70
what is the mass of a neutrino
0
71
does photon emission rate depend on intensity or frequency
intensity
72
if frequency increases and intensity remains constant, does photon emission rate increase or decrease?
decrease
However, when the frequency is changed, the definition of intensity comes into play. It does not mean the number of photons/second on a unit area. It is defined in terms of the energy arriving per second on a unit area. (ie power/unit area).
This means that if the frequency is increased, then the energy delivered by each photon increases. To have the same energy/power with more energetic photons, you need fewer of them.
73
what changes the stopping potential?
frequency (not intensity)
74
how is the size of an object determined by the retina?
The apparent size of the object is therefore not determined by the size of object itself, but by the angular size of the image formed on the retina (angle is bigger when object is closer, which makes it look bigger)
75
what is the process called accommodation used for?
The unaided eye can view objects at different distances through a process called accommodation
76
how does accommodation happen?
This is achieved by reshaping the crystalline lens located just behind the pupil by contraction of the eye muscles (the ciliary muscles) surrounding the lens. When the ciliary muscles are most relaxed, the eye focusses objects very (infinitely) far away. This infinite object distance is called the far point of human vision. To focus objects at closer distances, the ciliary muscles contract, thereby increasing the curvature of the lens and decreasing its focal length.
77
what is the far point?
This infinite object distance is called the far point of human vision.
78
what is the near point?
There is a biological limit to the degree of this muscular contraction, determining the lowest object distance (the near point) at which an object can be focussed by the eye. For normal human vision, this distance is approximately 25 cm.
79
why can we not observe the finer structures in biology at the near point?
For many applications, such as cell biology, this image is insufficiently large to resolve finer structures on the object.
80
what is the role of a magnifier?
The role of any visual magnifier is to increase the visual angle in order to resolve these finer structures
81
what is the angular magnification?
The degree of magnification (the angular magnification) is defined as the ratio of the visual angle obtained from the magnifier to that obtained from the unaided eye for an object at its near point
82
how does the simple magnifier work?
The simple magnifier consists of a single convex (converging) lens whose focal length is less than the near point of the eye. In the ideal case, the object is placed at the focal point of the lens, producing an image at infinity. This image presents a large visual angle to the eye. In addition, the magnifier further assists the eye by placing the viewed image at infinity (the far point) thus minimizing the strain on the ciliary muscles
83
what is the compound microscope?
By adding a second lens, the magnification can be further increased. In the typical arrangement (Fig. 3), this second lens (the objective) is placed near the microscope object (the specimen) at a distance slightly exceeding the objective’s focal length. The objective produces lateral magnification by forming a real image I1 that is larger than the object. The image created by the objective is also inverted. This inversion is observed as an overall effect when viewing through the microscope. The image formed by the objective acts as the object for the other lens (the eyepiece). Using the focussing mechanism of the microscope, the distance between two lenses is adjusted until the image of the objective falls in the focal plane of the eyepiece. The eyepiece, acting as a simple magnifier, provides the necessary angular magnification.
84
in the converging microscope, what is the difference between these 2 lenses?
objective lenses: produces a lateral magnification of the object, forming a real image that is larger than the object
eyepiece: image formed by objective lens is the object of the eyepiece. produces a lateral magnification. ideally, the image formed by the objective lens is on the focal point of the eyepiece. provides angular magnification
85
what is the total magnification of the microscope?
product of the magnification provided by each lens (Mobj x Meye)
86
why are there optical limits in the compound microscope?
because
87
what is image resolution?
Image resolution is the level of detail an image holds.
88
what is teta min (angular resolution)?
minimum angle between both light source coming from objects at which we can can distinguish the two objects
89
why does diffraction in the compound microscope limit our ability to see details?
Diffraction is the spreading of a wave as it passes through an aperture or around an obstacle. In an optical instrument, as the diffraction of light increases, the image formed by the instrument becomes more spread, which decreases the ability to resolve fine features of the specimen under view.
90
when is the critical angle obtained?
By Rayleigh’s Criterion, this critical angle is obtained when the central maximum of the diffraction intensity pattern for each source coincides with the first minimum of the pattern for the other source.
91
why are light microscopes limited in terms of resolution power?
We see from the formula for θmin that the resolution of the microscope can be improved by decreasing the wavelength of the illuminant. Visible light offers limited scope for this, having a relatively narrow wavelength range of 400 nm (violet) to 700 nm (red). Moving toward shorter wavelengths of electromagnetic radiation (UV, X- and gamma-rays) is often impractical due cell damage caused by the high energy concentration of such radiation.
92
why does using a stream of electrons as an illuminant give good resolution?
Particles also possess wave-like properties, with their wavelength given by λ = h/p, where p is the magnitude of the particle’s momentum, and h is a universal constant known as Planck’s constant. For instance, a travelling electron has a wavelength that is of the order of one- thousandth that of visible light. Consequently, electron illumination permits resolution of specimen features at one-thousandth the size that light illumination does
93
in an electron microscope, do we use optical lenses?
since optical lenses cannot be used to focus electron beams, the objective and eyepiece of an electron microscope consist of magnetic lenses that deflect a beam of travelling electrons on account of their charge
94
how does the electron microscope work?
95
what is the formula for the angular magnification?
M = θ/θo where the near point is 25 cm.
96
