Study Notes: SAT Physics Subject Test


Basic equation: \small v=\lambda f; \small \lambda =vT

Stretched String: \small v=\sqrt{\frac{F_{T}}{\mu}} (\small \mu=m/L)

Standing waves

Fundamental standing wave: \small f_{1}=\frac{v}{2L}

Standing wave: \small f_{n}=nf_{1}=\frac{nv}{2L}

Sound waves

Intensity: \small I=\frac{P}{A} (P is the power produced by the source and A is the area over which the power is spread.)

Decibel level: \small \beta=10log(\frac{I}{I_{0}}) (\small I_{0}=10^{-12}W/m^{2})

Beat: \small f_{\text{beat}}=|f_{1}-f_{2}|

Resonance for sound waves

If the far end of tube is sealed, for any odd integer n: \small \lambda_{n}=\frac{4L}{n}, \, f_{n}=n \frac{v}{4L}

If the far end of tube is not sealed, for any integer n: \small \lambda_{n}=\frac{2L}{n}, \, f_{n}=n \frac{v}{2L}

The Doppler effect

The shift in frequency that occures when the source and detector are in relative motion is known as the Doppler effect.

\small f_{D}=\frac{v \pm v_{D}}{v \mp v_{S}} \cdot f_{s}

When a detector approaches a source or a source approaches a detector, the resulting frequency would increase and vice versa.

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Siujoeng Lau

Liberty will never perish.

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