Grade 10 general science – Waves Quiz

A wave is a disturbance that carries energy (and momentum) through a medium or space while the medium's particles generally oscillate about fixed positions rather than being transported permanently.

Mechanical waves, such as sound, require a material medium (air, water or solid) to travel. Electromagnetic waves like light, radio and gamma rays do not require a medium.

In transverse waves particles oscillate perpendicular to the direction of wave propagation (example: water surface waves), while in longitudinal waves oscillation is parallel (example: sound in air).

Surface water ripples are transverse: water particles move up and down while the wave travels horizontally. Sound and pressure waves are longitudinal; P-waves are longitudinal seismic waves.

Wavelength is a spatial measure: distance between successive identical points (crest to crest or trough to trough) on a wave.

Period T is the time for one oscillation; frequency f is number of oscillations per second, so f = 1/T with SI unit hertz (Hz).

Wave speed equals frequency times wavelength (v = fλ). This applies to all waves, including sound and electromagnetic waves.

Frequency is measured in hertz (Hz), which equals one oscillation per second (s⁻¹).

Sound is a mechanical longitudinal wave that requires particles in a medium to transmit pressure variations; it cannot travel through empty space.

Human perception of pitch rises with frequency: higher frequency sound waves are heard as higher pitch.

Loudness depends mainly on the amplitude (and intensity) of the sound wave: larger amplitude means more energy and a louder sound.

The law of reflection states that for smooth surfaces the angle measured from the normal to the incident ray equals the angle from the normal to the reflected ray.

Refraction is bending of a wave when it changes speed crossing into a medium with different properties (e.g., air to water), causing a change in direction.

Diffraction (bending around obstacles) is most significant when the obstacle or aperture size is similar to the wavelength; for example low-frequency sounds diffract around buildings.

Constructive interference occurs when two waves meet in phase so their displacements add, producing a resultant wave with greater amplitude.

Nodes are positions on a standing wave that remain fixed (zero displacement) due to continuous destructive interference of incident and reflected waves.

Resonance occurs when a periodic driving force matches a system's natural frequency, causing large amplitude oscillations (useful in musical instruments and sometimes destructive in bridges).

The Doppler effect causes an apparent increase in frequency (pitch) when the source approaches and a decrease when it recedes, as with moving sirens or vehicles.

All electromagnetic waves (radio, light, X-rays) travel at the constant speed c in vacuum (~3.00×10^8 m/s) independent of frequency. They do not need a medium.

Period T is the time for one full cycle of oscillation at a fixed point; its reciprocal is frequency (f = 1/T).

Wavelength is the spatial distance from one crest to the next (or trough to trough), not the vertical crest-to-trough distance which is related to amplitude.

In transverse waves particles oscillate perpendicular to the direction the wave energy travels; the wave carries energy along its propagation direction.

Ultrasound uses high-frequency sound waves for safe imaging in medicine (prenatal scans, organ checks) and is widely used in hospitals across Kenya and the world.

As sound radiates from a source, its energy spreads over a larger area, reducing intensity per unit area (approximately following an inverse-square dependence for a point source).

Sound speed depends on medium properties (elasticity and density) and temperature; typically sound travels fastest in solids, slower in liquids, and slowest in gases, and increases with temperature in gases.