Study Notes: SAT Physics Subject Test

Modern Physics

The energy of a photon: \small E=hf (h is Planck’s constant)

de Broglie wavelength: \small \lambda = \frac{h}{p} = \frac{h}{mv}

Radioactivity

Alpha decay: \small ^{A}_{Z}X \to ^{A-4}_{Z-2}X' + ^{4}_{2}\alpha

\small \beta^{-} decay: \small ^{14}_{6}C \to^{14}_{7}N + ^{0}_{-1}e + \vec{V_{e}}

\small \beta^{+} decay: \small ^{17}_{9}F \to^{17}_{8}O + ^{0}_{+1}e + V_{e}

Electron Capture: \small ^{7}_{4}Be  + ^{0}_{-1}e \to ^{7}_{3}Li + V_{e}

Gamma decay: \small ^{42}_{20}Ca^{*} \to ^{42}_{20}Ca + \gamma

Radioactive decay rates: \small A=A_{0}e^{-\lambda t}

Special relativity

Postulate 1: All the laws of physcis are the same in all inertial reference frames.

Postulate 2: the speed of light in vacuum always has the same value, regardless of the motion of the source or the observer.

Relativistic factor: \small \gamma=\frac{1}{\sqrt{1-(\frac{v}{c})^{2}}}

Velocity: \small v_{\text{you}}=\frac{u+v}{1+uv/c^{2}}

Time: \small \Delta T_{2}=\gamma \Delta T_{1}

Length: \small L_{2}=\frac{L_{1}}{\gamma}

Energy: \small KE=(\gamma -1)mc^{2}

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Siujoeng Lau

Liberty will never perish.

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