Waves & Sound — Physics for MCAT

Wave properties:

Wavelength (λ), frequency (f), amplitude, period (T = 1/f)

Speed: v = fλ

Speed of sound in air ~340 m/s; in water ~1500 m/s; faster in denser media

Speed of light = 3×10⁸ m/s (in vacuum)

Transverse vs. Longitudinal:

Transverse — wave perpendicular to motion (light, EM waves)

Longitudinal — wave parallel to motion (sound)

Sound intensity:

Measured in decibels (dB): β = 10 log(I/I₀)

I₀ = 10⁻¹² W/m² (threshold of hearing)

10× intensity = 10 dB increase

Doppler effect:

Source moving toward observer → higher perceived frequency (blue shift)

Source moving away → lower frequency (red shift)

Used in medical ultrasound to measure blood flow velocity

Ultrasound: f > 20,000 Hz. Diagnostic imaging uses 1–20 MHz. Reflection at tissue boundaries creates images. Used for OB/GYN, cardiac imaging, vascular studies.

Reference:

Wikipedia: Sound

https://en.wikipedia.org/wiki/Sound