Waves 1

Sound wave

A longitudinal wave that travels through a medium by particle vibrations.

Human hearing range

20 Hz to 20,000 Hz.

Longitudinal wave

A wave where vibrations are parallel to the direction of energy transfer.

Transverse wave

A wave where vibrations are perpendicular to the direction of energy transfer.

Slinky (transverse)

Side-to-side motion used to model transverse waves.

Slinky (longitudinal)

Push-and-pull motion used to model longitudinal waves.

Ultrasound

Sound waves with frequencies above 20,000 Hz.

Ultrasound uses

Medical imaging, sonar, and industrial testing.

Ultrasound distance equation

Distance = (speed × time) ÷ 2.

Wave speed equation

v = f × λ.

v (wave speed)

Measured in meters per second (m/s).

f (frequency)

Measured in hertz (Hz); waves per second.

λ (wavelength)

Distance between two corresponding points of a wave (m).

Ripple tank

Used to measure wave speed and properties in water.

Wave practical (liquid)

Use strobe to measure wavelength and count frequency; apply v = f × λ.

Wave practical (solid)

Use string/slinky, measure wavelength, time vibrations to get frequency.

Reflection

Wave bounces off a surface; angle of incidence = angle of reflection.

Specular reflection

Reflection from a smooth surface, producing a clear image.

Diffuse reflection

Reflection from a rough surface; rays scatter, no image formed.

Refraction

Bending of waves due to a change in speed when entering a new medium.

Refraction towards normal

Occurs when wave slows down (e.g. air → glass).

Refraction away from normal

Occurs when wave speeds up (e.g. glass → air).

Ray diagram

Diagram showing direction of wave with rays and normal line.

Diffraction

Spreading of waves when they pass through a gap or around an obstacle.

More diffraction

Occurs when wavelength is similar to or larger than the gap.

Less diffraction

Occurs when wavelength is much smaller than the gap.

Ear drum

Part of the ear that vibrates in response to sound waves.

Cochlea

Part of the inner ear that converts vibrations into electrical signals.

Speed of sound in air

Approximately 330 m/s.

Wave period

The time for one complete wave to pass a point (T = 1/f).