Sound — MHT-CET Physics

Formulas (1)

• Speed, Energy and Decibels · Wave speed and loudness
  $$v = f\lambda, \qquad L = 10\log_{10}\frac{I}{I_0}$$

Watch out for (2)

• Treating decibels as linear
  → Speed, Energy and Decibels
• Holding amplitude fixed when frequency changes
  → Speed, Energy and Decibels

Formulas (2)

• Open and Closed Pipes · Pipe frequencies
  $$f_{\text{open}} = \frac{nv}{2L}, \qquad f_{\text{closed}} = \frac{(2n - 1)v}{4L}$$
• Resonance Tubes, Strings and Beats · Strings and beats
  $$f_n = \frac{n}{2l}\sqrt{\frac{T}{\mu}}, \qquad f_{\text{beat}} = |f_1 - f_2|$$

Watch out for (6)

• Numbering overtones as harmonics
  → Open and Closed Pipes
• Allowing even harmonics in a closed pipe
  → Open and Closed Pipes
• Adding one end correction to an open pipe
  → Open and Closed Pipes
• Reporting mass per unit length as the mass
  → Resonance Tubes, Strings and Beats
• Adding frequencies to get beats
  → Resonance Tubes, Strings and Beats
• Taking the first resonance for the least water
  → Resonance Tubes, Strings and Beats

Formulas (2)

• The Doppler Formula · Doppler effect
  $$f' = f\,\frac{v \pm v_o}{v \mp v_s}$$
• Passing Sources, Echoes and Changing Speeds · Echo from a wall
  $$n' = n\,\frac{v + V_1}{v - V_1}$$

Watch out for (4)

• Treating moving source and moving observer alike
  → The Doppler Formula
• Getting the sign for recession
  → The Doppler Formula
• Using the source formula twice for an echo
  → Passing Sources, Echoes and Changing Speeds
• Using one Doppler factor for before and after a pass
  → Passing Sources, Echoes and Changing Speeds