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# Year 12 Physics

## Module 7 | The nature of light

### Content 4: Light and special relativity

#### Lesson 1 | Relative simultaneity

• analyse and evaluate the evidence confirming or denying Einstein’s two postulates:
– the speed of light in a vacuum is an absolute constant
– all inertial frames of reference are equivalent (ACSPH131)

#### Lesson 2 | The consequences of relativistic travel

• investigate the evidence, from Einstein’s thought experiments and subsequent experimental validation, for time dilation ($t = \frac{t_{0}}{\sqrt{\left ( 1-\frac{v^{2}}{c^{2}} \right )}}$) and length contraction ($l = l_{0}\sqrt{\left ( 1-\frac{v^{2}}{c^{2}} \right )}$), and analyse quantitatively situations in which these are observed, for example:
– observations of cosmic-origin muons at the Earth’s surface
– atomic clocks (Hafele–Keating experiment)
– evidence from particle accelerators
– evidence from cosmological studies

• describe the consequences and applications of relativistic momentum with reference to:
$p_{v} = \frac{mv}{\sqrt{(1-\frac{v^{2}}{c^{2}})}}$
– the limitation on the maximum velocity of a particle imposed by special relativity (ACSPH133)

• use Einstein’s mass–energy equivalence relationship (E = mc2) to calculate the energy released by processes in which mass is converted to energy, for example: (ACSPH134)
– production of energy by the sun
– particle–antiparticle interactions, eg positron–electron annihilation
– combustion of conventional fuel