The Muon Experiment:
Evidence: Muons are observed on the surface of the Earth.
Inference: Time dilation and Length contraction has taken place because the Muons would otherwise decay only after 1 kilometre.
Monday, March 28, 2011
Sunday, March 27, 2011
H4
The Twin Paradox:
There are 2 identical twins named Anantha and Ahtnana.
Anantha sees Ahtnana's clock tick more slowly than her own, so he things that Ahtnana is ageing more slowly than Ahtnana is. Anantha therefore expects that when Ahtnana returns,Ahtnana will be the younger.
Ahtnana sees Anantha's clock tick more slowly than her own so thinks a is aging more slowly. B therefore expects that Anantha will be younger when he returns.
The Paradox is that they cannot both be the younger one out of the two.
So who is actually the youngest?
Since Ahtnana had to accelerate when he started, when he turned around to come home, and when she stopped at the end. Ahtnana is therefore in a non-inertial frame of reference, so the problem can't be solved with special relativity. General Relativity shows that during acceleration, clocks also tick slowly so B will in fact be the younger out of the 2.
What was Developed to satisfy the Twin Paradox?
The General Theory of Relativity was invented and it satisfied the Paradox as the General Theory took non-inertial frames of reference into account and is able to deal with them.
Hafele-Keating Experiment:
Question 7,8 and 9:
There are 2 identical twins named Anantha and Ahtnana.
Anantha sees Ahtnana's clock tick more slowly than her own, so he things that Ahtnana is ageing more slowly than Ahtnana is. Anantha therefore expects that when Ahtnana returns,Ahtnana will be the younger.
Ahtnana sees Anantha's clock tick more slowly than her own so thinks a is aging more slowly. B therefore expects that Anantha will be younger when he returns.
The Paradox is that they cannot both be the younger one out of the two.
So who is actually the youngest?
Since Ahtnana had to accelerate when he started, when he turned around to come home, and when she stopped at the end. Ahtnana is therefore in a non-inertial frame of reference, so the problem can't be solved with special relativity. General Relativity shows that during acceleration, clocks also tick slowly so B will in fact be the younger out of the 2.
What was Developed to satisfy the Twin Paradox?
The General Theory of Relativity was invented and it satisfied the Paradox as the General Theory took non-inertial frames of reference into account and is able to deal with them.
Hafele-Keating Experiment:
Question 7,8 and 9:
Monday, March 21, 2011
H3
H 3.1
Light Clock:
Describe the observations either Jack and Jill or observer A and B:
Observer A and B both have light clocks that time 1 nanosecond for every time light reflects through a cycle.
But observer B is inside a glass carriage travelling at velocity v relative to observer A. Because the carriage is moving relative to observer A, the distance travelled is greater, but the speed of light is still c (the same in all inertial frames).
Therefore the time between the light leaving the lower surface and returning must now be greater than a nanosecond.
Define Light clock:
A light clock is a clock in which a pulse of light is sent and reflected off glass and returns to the point the pulse was given from.
Lorenz Factor Graph:
Light Clock:
Describe the observations either Jack and Jill or observer A and B:
Observer A and B both have light clocks that time 1 nanosecond for every time light reflects through a cycle.
But observer B is inside a glass carriage travelling at velocity v relative to observer A. Because the carriage is moving relative to observer A, the distance travelled is greater, but the speed of light is still c (the same in all inertial frames).
Therefore the time between the light leaving the lower surface and returning must now be greater than a nanosecond.
Define Light clock:
A light clock is a clock in which a pulse of light is sent and reflected off glass and returns to the point the pulse was given from.
Lorenz Factor Graph:
Wednesday, March 16, 2011
Relativity
Define a frame of reference:
A frame of reference is a system of coordinates that enables the position of various objects to be specified.
Define Galilean transformation:
Galilean transformation are made under the assumptions that time measurement (and space measurements) are independent of the observer.
G3 Questions:
a) A Galilean transformation are made under the assumptions that time measurement (and space measurements) are independent of the observer.
b) i) 1.96c
G1 Questions:
a) 1.90c
E 6.4 - E 6.7
E 6.4
State Hubble's law
V = Ho d
E 6.5
Discuss the limitations of Hubble's law:
Hubble's law predicts that the recessional velocity of the galaxy will be Hx. the assumption is that the universe is travelling at this constant speed since the beginning of the Universe. However, the gravitational attraction between galaxies means that the speed of recession decreases cosntantly. The fact that we assume that the recession velocity is constant, is a limitation of Hubble's law. Also, the data points in the graph below are scattered around the trend line thus showing that there are quite big random errors in the measurements.
State Hubble's law
V = Ho d
E 6.5
Discuss the limitations of Hubble's law:
Hubble's law predicts that the recessional velocity of the galaxy will be Hx. the assumption is that the universe is travelling at this constant speed since the beginning of the Universe. However, the gravitational attraction between galaxies means that the speed of recession decreases cosntantly. The fact that we assume that the recession velocity is constant, is a limitation of Hubble's law. Also, the data points in the graph below are scattered around the trend line thus showing that there are quite big random errors in the measurements.
Monday, March 14, 2011
E6
E 6.1
Describe the distribution of galaxies in the universe
Define the term galactic cluster:
Describe the distribution of galaxies in the universe
Define the term galactic cluster:
- A cluster of roughly a few hundred young stars in a loose distribution. Also called an open cluster. Source: Encyclopaedia.com
Define the term galactic super-cluster:
- Superclusters are large groups of smaller galaxy groups and clusters and are among the largest structures of the cosmos. Source: en.wikipedia.org/wiki/Galactic_supercluster
Source: http://www.dragonslain.com/large_clusters.gif
E6.2
Explain the red-shift of light from different galaxies
Why are galaxies that are the furthest away red-shifted the most? :
- Because the universe is constantly expanding the the galaxies which are on the outer part of the big bang are moving away from the centre the fastest.
Sunday, March 13, 2011
12.3
Outline the reasons for power losses in transmission lines and real transformers
Resistance of a transformer result in the transformer heating up.
Eddy currents. The currents can be reduced by laminating the core into individually electrically insulated thin strips.
Hysteresis losses causes the iron core to warm up due to the continued cycle of changes to its magnetism.
Flux losses are caused by magnetic leakage. A transformer is only 100% efficient if all of the magnetic flux that is produced by the primary links with the secondary.
E 3.1 - E 3.8
E 3.1
Define the parsec
"A unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years"
Source: wordnetweb.princeton.edu/perl/webwn
Define the parsec
"A unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years"
Source: wordnetweb.princeton.edu/perl/webwn
Wednesday, March 9, 2011
E5
Describe the conditions that initiate fusion in star:
Stars are formed when large clouds of gas and dust are compressed. The cannot form on their own because the gravitational force is not big enough to pull the particles together. A large supernova or a collision with another star will cause the process to occur.
State the effect of a star's mass on the end product of a nuclear fusion:
Stars are formed when large clouds of gas and dust are compressed. The cannot form on their own because the gravitational force is not big enough to pull the particles together. A large supernova or a collision with another star will cause the process to occur.
State the effect of a star's mass on the end product of a nuclear fusion:
- A star will eventually start fusing helium and hydrogen will become rare.
- Fusion reactions will then happen less often The core of the star will begin to collapse as the star is no longer in equilibrium.The collapse of the star increases its core temperature. Because of the higher pressure and temperature
- in the core helium fusion is now possible
Monday, March 7, 2011
E 4.8 - E 4.10
Graph showing the 3 possible fates of the Universe:
Taken from Chris Hamper's Physics texbook for the IB
Definitions of the three possible fates:
- Open universe
- The density of the Universe is lower than the critical density therefore the universe continues to expand
- Flat universe
- The density of the Universe is exactly at the critical density therefore the universe ceases to expand or contract.
- Closed universe
- The density of the Universe is greater than the critical density, therefore the universe would contract and may in turn lead to a "Big-crunch".
Definition of Critical Density:
- The Critical Density is the exact density of the universe required for the fate of the universe to neither expand or contract (flat fate).
How does the density of the Universe relate to its fate in terms of the critical density?:
- The density of the Universe is the deciding factor when you consider its fate in the long run. We deduce the fate of the universe by comparing its density to the critical density. If the density of the Universe is over the critical density the the universe will contract and collapse into singularity. If the density of the universe is lower than the critical density then the universe will continue to expand. If the critical density and density of the universe are identical the universe will stop expanding and turn static. Although this is highly unlikely as the density of the universe has to match the critical density EXACTLY.
Sunday, February 20, 2011
E 1.1
E1.1
17D Homework sheet
Q1.
17D Homework sheet
Q1.
E1.2
Distinguish between a stellar cluster and a constellation.
A constellation is an arrangement of stars as viewed from planet earth, and a star cluster is just any random group of stars
E1.3
Pneumonic for the planets in our solar system
My Very Evil Mother Just Shot Uncle Ned
E1.4
Monday, January 31, 2011
13.2.3 - 13.2.4
13.2.3
Describe one piece of evidence for the existence of nuclear energy levels:
The energies of both alpha and gamma are discrete and have only certain values. Since these discrete energies come from the nucleus, it must mean that the nucleus has discrete nuclear energy levels (just like electrons do).
13.2.4
Describe β+ (positron) decay, including the existence of the neutrino:
When energy calculations were done with radioactive beta emissions, it was observed that the beta particles had lesser kinetic energy than they would have expected (after using more detailed levels of calculations). This opposed the law of conservation of energy as the energy had to come from somewhere. In 1930, Wolfgang Pauli said that there was a very small particle that therefore carried away this missing kinetic energy and momentum. This particle was named the neutrino.
Describe one piece of evidence for the existence of nuclear energy levels:
The energies of both alpha and gamma are discrete and have only certain values. Since these discrete energies come from the nucleus, it must mean that the nucleus has discrete nuclear energy levels (just like electrons do).
Describe β+ (positron) decay, including the existence of the neutrino:
When energy calculations were done with radioactive beta emissions, it was observed that the beta particles had lesser kinetic energy than they would have expected (after using more detailed levels of calculations). This opposed the law of conservation of energy as the energy had to come from somewhere. In 1930, Wolfgang Pauli said that there was a very small particle that therefore carried away this missing kinetic energy and momentum. This particle was named the neutrino.
13.2.1 - 13.2.2
13.2.1:
Explain how the radii of nuclei may be estimated from charged particle scattering experiments:
In charged particle scattering experiments, the particle that is repelled straight back will be at rest for a very short amount of time before it changes direction and travels back to where it came from. Rutherford proposed that this piece of information can be used to calculate and find the approximate size of the nucleus. This is because at that point in time where the particle is at rest with a velocity of 0, its kinetic energy will be exactly balanced out by its
electrical potential energy due to the electrostatic force which repels the nuclei.
13.2.2:
Describe how the masses of nuclei may be determined using a Bainbridge mass spectrometer:
Explain how the radii of nuclei may be estimated from charged particle scattering experiments:
In charged particle scattering experiments, the particle that is repelled straight back will be at rest for a very short amount of time before it changes direction and travels back to where it came from. Rutherford proposed that this piece of information can be used to calculate and find the approximate size of the nucleus. This is because at that point in time where the particle is at rest with a velocity of 0, its kinetic energy will be exactly balanced out by its
electrical potential energy due to the electrostatic force which repels the nuclei.
13.2.2:
Describe how the masses of nuclei may be determined using a Bainbridge mass spectrometer:
A magnetic field is used to deflect the ions of a substance. If the ions have the same charge they will have the same velocity. The radius of their circular path however depends on how heavy that particular ion is. A larger mass ion will travel a larger distance (larger circle radius). Therefore, the masses of nuclei may be determined using a Bainbridge mass spectrometer.
Monday, January 24, 2011
Nelson Questions
19.4
Max Kinetic Energy = hf - ɸ
= (6.63x10^-34 x 3.19x10^-9) - 3.413x10^-19
= -3.8x10^-19
Since Kinetic energy = Vsq
3.8x10^-19/9.1x10^-31 = 4.176x10^11 eV
19.5
Max Kinetic Energy = hf - ɸ
2.4x10^-19 = 6.63x10^-34 x (3x10^8/500x10^-9) -
ɸ = 1.56x10^-19
Max Kinetic Energy = hf - ɸ
= (6.63x10^-34 x 3.19x10^-9) - 3.413x10^-19
= -3.8x10^-19
Since Kinetic energy = Vsq
3.8x10^-19/9.1x10^-31 = 4.176x10^11 eV
19.5
Max Kinetic Energy = hf - ɸ
2.4x10^-19 = 6.63x10^-34 x (3x10^8/500x10^-9) -
ɸ = 1.56x10^-19
Sunday, January 16, 2011
12.2.1 to 12.2.5
12.2.1
Describe the emf induced in a coil rotating within a uniform magnetic field
Describe the emf induced in a coil rotating within a uniform magnetic field
12.2.2
Explain the operation of a basic alternating current (ac) generator
- A coil of wire rotates in the magnetic field due to an external force. As it rotates, the flux linkage of the coil changes with time and induces and e.m.f (refer to Faraday's law) causing current to flow.
- Sides the 2 sides parallel with the magnet will experience a force opposing the motion. (refer to Lenz's Law)
- The work done rotating the coil generates electrical energy.
12.2.3
Describe the effect on the induced emf of changing the generator frequency
- The speed of rotation is changed it will affect:
Time (distance between peaks)
EMF (amplitude of peaks) - For example, if the speed is doubled therefore, the time period will be halved and the EMF (amplitude) will be doubled.
12.2.4
Discuss what is meant by the root mean squared (rms) value of an alternating current or voltage
- When the output of an a.c. generator is connected to a resistor, an alternating current will flow. A sinusoidal potential difference means a sinusoidal current.
Thursday, January 13, 2011
12.1.1 to 12.1.4
12.1.1 Describe the inducing of an emf by relative motion between a conductor and a magnetic field:
12.1.2 Derive the formula for the emf induced in a straight conductor moving in a magnetic field:
12.1.3 Define Magnetic Flux and Magnetic Flux Linkage:
12.1.4 Describe the production of an induced emf by a time-changing magnetic flux:· An e.m.f. is also produced in a wire if the magnetic field changes with time. The universal rule that applies to all situations involving emf is stated as: "the magnitude of an induced e.m.f is proportional to the rate of change of flux linkage"
State Faraday's law and Lenz's law:· Faraday's law:
· Lenz's law states that "The direction of the induced e.m.f. is such that if an induced current were able to flow, it would oppose the change which caused it". QuestionsQ39 a) emf = BLv =50x10^-6 x 0.2 x 20 = 2 x 10^-45b) I = V / R I=2x10^-4 / 2 = 1x10^-4c) I^2 R = 1 x 10^-4 x 2 = 2 x 10^-8 Wd) Work done = energy dissipated = 2 X 10^-8e) s = d/t s = 20/1 = 20m/sf) F = work / d = 2x10^-8/20 = 1x10^-9
Q40 a) Total flux = 5000 x 10^-6 x 2 x 10^-4 = 1 x 10^-6 2 x 10^-4 m^2 = 2 cm^2b) would be a quarter since flux density would be halved and time would be doubled= 0.25 X 10^-6tm^-2s^-1c) since induced emf = rate of change of flux, the induced emf is 0.25 x 10^-6 V
Q41 a) = 6 x 10^-4 x 50 x 500 x 10^-6 therefore total flux = 1.5 x 10^-5 tm^-2b) Φ = BcosθxAΦ = 500 x 10^-6 x cos30 x 6x10^-4 x 50 Φ = 1.3 x 10^-5 tm^-2 c) Blv = tm^2/s1.3 x 10^-5 / 3 = 4.3 x 10^-6 V |
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