An "evaluate" question.. need answers (1 Viewer)

[kooltrainer]

this is an 6 mark question so make sure u answer as much as u can

Q: Evaluate the michelson-morley experiment
A : ?

need help plz.. i cant seem to write anything
Also, another question. From the length contraction formula, is the length measure in cms? m? .. the book doesnt say.. so does it mean if question gives proper length in millimetres, the contracted length is also in millimetres?

 

[Mark576]

Evaluate: Make a judgement based on criteria ...This should help you.

The textbook doesn't say because it doesn't matter as long as you're consistent. So yes, if you use millimetres as the rest length, then the relativistic length will also be in millimetres.

Yeah sorry about the shortened answer, I'm a little busy and what I've given you should help anyway.

 

[powerdrive]

This question is pretty much the Space 4.2 dotpoint. Here is one source:

Space 4.2 Describe and evaluate the Michelson-Morley attempt to measure the relative velocity of the earth through the aether.

The​

Michelson-Morley experiment was designed to see if
the aether did exist.
The aether supposedly existed in space, and the earth spins
at about 30 km h-1. Therefore, if the aether did exist, the
earth should experience an aether wind just like a swimmer
swimming across a current and light should be slowed down
when travelling into the ‘wind.’
A light ray was shone into the half-silvered mirror. Ray 1
heads on into the aether, then reflects off Mirror M1, reflects
off the central mirror and finished at T.
Ray 2 is reflected from the central mirror towards mirror M2.
It is reflected off mirror M2, before returning to T.
An inference pattern was shown for both rays when they
reached the inferometer at T. The whole apparatus was
rotated by 90° with the idea being that the aether wind would
cause a change in the inference patterns.
The experiment was also repeated over various stages of
the year, during different seasons.
The result was that the inference patterns were the same for​

each attempt and the experiment was given a null result.


I've attached another source too, and it includes a sample exam response. Hope it helps.

With measurements, yeh just make sure you're consistent throughout the problem. Generally u use metres (standard SI units) through hsc physics.

 

[kooltrainer]

oohh.. nice, thx
Also,
Q: it was 50 years before experimental evidence was available to support Eintein's theory of relativity. Outline one piece of evidence in support of his theory.

 

[powerdrive]

4. analyse information to discuss the relationship between theory and the evidence supporting it, using Einstein‟s predictions based on relativity that were made many years before evidence was available to support it

Experimental evidence for time dilation on the macroscopic level can be seen by synchronising two atomic clocks, leave one on Earth and send the other around the Earth in a jet at high speeds, and in the opposite direction to the rotation of the Earth (to maximise the relative velocity). When the two clocks are brought back together, the one left on Earth should have recorded more time to have passed than the other clock. This is because the clock on the rocket was travelling at a faster speed and so time dilation has caused the time to slow.

Another piece of experimental evidence on the microscopic level is the time dilation of muons. When high-energy particles from space hit the Earth‟s atmosphere, subatomic particles called muons are produced. Muons are unstable and have only a very short lifetime before they decay. The rest time of these particles is about 2 microseconds. With this lifetime, even if they travelled at speeds near the speed of light, they could only travel 600m before decaying (without taking into account special relativity). Yet muons are seen on the Earth‟s surface, which is about 10 km of distance from when they were produced. The reason they make it this far is that as these particles are moving so fast, time passes much more slowly for them as observed by us. Length contraction also provides an alternative, equivalent explanation of why these muons can reach the Earth‟s surface before they decay. From the muons frame of references, the Earth is rushing towards them at a speed close to the speed of light. And so the Earth‟s atmosphere has

 

[Steth0scope]

kooltrainer.

Have ya got the notes off Charles Sturt yet. If not:

http://hsc.csu.edu.au

Very, very very very very helpful.

GL

 

[mattzada]

Michelson-Morley

My Trial Answer to:

Describe and Evaluate the Michelson-Morley attempt to measure the relative velocity of the Earth through the aether.

When two boats are raced in a river, the boat travelling across the current always wins the race, as opposed to the boat travelling with or against the current.

Michelson-Morley's attempt to measure the velocity of the Earth through the Aether was based on a similar concept. They tried to measure the velocity of light, since the light travelling across the aether should always win.

When they rotated their apparatus 90 degrees, no change in the interference pattern was observed. Hence, they received a null result.

The experiment was retried several times by other scientists, at different times, altitudes, with more sensitive equipment, etc. Regardless of all changes, they received a null result and so the experiment failed to detect the aether.

Suggested Answer

Evaluation: The MM experiment was immensely important, providing evidence that there is no aether and that the speed of light is constant.

Description: Coherent monochromatic beams were raced over identical distances. If Earth moves through the aether, different effective path lengths will produce changes in the interference patterns as the beams merge. No matter the orientation of the apparatus, no change in the interference pattern was ever detected. Hence, a null result.

 

[kooltrainer]

4. analyse information to discuss the relationship between theory and the evidence supporting it, using Einstein‟s predictions based on relativity that were made many years before evidence was available to support it

Experimental evidence for time dilation on the macroscopic level can be seen by synchronising two atomic clocks, leave one on Earth and send the other around the Earth in a jet at high speeds, and in the opposite direction to the rotation of the Earth (to maximise the relative velocity). When the two clocks are brought back together, the one left on Earth should have recorded more time to have passed than the other clock. This is because the clock on the rocket was travelling at a faster speed and so time dilation has caused the time to slow.

Another piece of experimental evidence on the microscopic level is the time dilation of muons. When high-energy particles from space hit the Earth‟s atmosphere, subatomic particles called muons are produced. Muons are unstable and have only a very short lifetime before they decay. The rest time of these particles is about 2 microseconds. With this lifetime, even if they travelled at speeds near the speed of light, they could only travel 600m before decaying (without taking into account special relativity). Yet muons are seen on the Earth‟s surface, which is about 10 km of distance from when they were produced. The reason they make it this far is that as these particles are moving so fast, time passes much more slowly for them as observed by us. Length contraction also provides an alternative, equivalent explanation of why these muons can reach the Earth‟s surface before they decay. From the muons frame of references, the Earth is rushing towards them at a speed close to the speed of light. And so the Earth‟s atmosphere has

ty.. when it says to provide evidence for theory of relativity.. do we only talk abt time dilation.. wot abt in general and other dilations?? Or is it okay to just talk abt time dilation and that'll be enough.

 

[mattzada]

analyse information to discuss the relationship between theory and the evidence supporting it, using Einstein’s predictions based on relativity that were made many years before evidence was available to support it

A proposed theory usually needs experimental evidence before it is taken seriously

Einstein proposed his theory of special relativity in 1905 and theory of general relativity in 1915. There was no evidence available to prove his theory apart from observations of star light passing close to the sun at the time of a solar eclipse. A slight shift in position of a star could be accounted for by general theory

• As technology improved other evidence became available such as:
  • flying atomic clocks to determine existence of time dilation
  • dilated lifetime of mesons penetrating Earth's atmosphere
  • energy yield from converted mass in nuclear reactions
  • observed increase in mass of particles accelerated near c in particle accelerators

As a consequence of relativity theory successes with experimental evidence, the existence of the aether has been shown to no longer be required.

 

[powerdrive]

ty.. when it says to provide evidence for theory of relativity.. do we only talk abt time dilation.. wot abt in general and other dilations?? Or is it okay to just talk abt time dilation and that'll be enough.

just provide experimental examples, say 2 or 3 (really it depends on how many marks the question is worth), and talk about the appropriate relativity principles. like in the muon one, if u read it, it talks about time dilation and length contraction.

look into the examples mattzada has provided, they show experimental evidence for all the principles