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this is prob gonna sound really dumb... (1 Viewer)

acullen

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peeasoup, you have got to be joking! I seem to remember that it was one of the first things we learnt in Physics. Remember the concept of 'relativistic velocity'? Well that's why the speed of light is always constant; time dialates so that the speed of light is always constant at 2.99m/s (or 3.00m/s in the formula sheet - argh) from any frame of reference. Although now there is very recent speculation as to whether Einstein was actually correct in stating the speed of light is constant. This has parallels to the concept of Cooper Pairs in semiconductors: it was proven incorrect in January this year; however, despite this: it is what you must learn and convey that you understand it to the examiner. As far as the syllabus and the HSC course is concerned: the speed of light is always constant from any frame of reference.

Seeing you don't believe the 15 or so people that have informed you otherwise, here are some quotes:

The constancy of the speed of light depends on the uncertainty principle and what is known as the Lorentz invariance, a fundamental principle of Einstein's special theory of relativity that states the laws of physics - including the speed of light - are same everywhere.
Sourced from: http://www.space.com/scienceastronomy/lightspeed_031217.html

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It is important to realize that the speed of light is not a "speed limit" in the conventional sense. An observer chasing a beam of light will measure it moving away from him at the same speed as a stationary observer.
Sourced from: http://en.wikipedia.org/wiki/Speed_of_light#Constant_in_all_reference_frames

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...and finally and most importantly, the HSC syllabus:
describe the significance of Einstein’s
assumption of the constancy of the
speed of light
Sourced from: "HSC Syllabus: Section 4 - Students learn to: (point f)" http://www.boardofstudies.nsw.edu.au/syllabus_hsc/pdf_doc/physics_stg6_syl_03.pdf
 
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pc_wizz

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heh ... peeasoup has no clue, bloody hilarious! ... :p
 

rumour

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I didn't read the other answers in case I got confused & I just did the speed of light is constant one!!!!!!!!
 

gordo

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its actually not constant, unless the air atmosphere and molecules in each space craft was the same and they had the exam same glass windows.
when the light wave permeates both windows and the air within both space craft, for the ray to travel to the observors eye and for them to see it, the wave will slow down due to the different refractive indexes of the materials and the path it transcribe through different densitys of molecules

light is only constant if it is travelling through the same medium for both observers

so techinically, u didn't have enough information i guess :D
 

acullen

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gordo said:
its actually not constant, unless the air atmosphere and molecules in each space craft was the same and they had the exam same glass windows.
when the light wave permeates both windows and the air within both space craft, for the ray to travel to the observors eye and for them to see it, the wave will slow down due to the different refractive indexes of the materials and the path it transcribe through different densitys of molecules
I don't think they expect you to take into consideration the refractive indexes of minute things. :p How do we know that the light source on spaceship Beta isn't an external light and that observer on spaceship alpha isn't measuring the speed of light through instrumentation mounted on the exterior of the spaceship?

I think you can clearly state that "(A) The speed of light beam is equal to c." is the most correct answer. :p
 

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