Wave Physics Quiz25 Questions with Instant Answers & Explanations

• AThe maximum displacement of the medium from its rest positionCorrect
• BThe distance between two consecutive crests
• CThe number of cycles passing a point each second
• DThe speed at which the wave pattern travels

Amplitude is how far the medium is displaced from equilibrium at the peak of its oscillation. It sets the energy the wave carries, not its speed — the distance between crests is wavelength, and cycles per second is frequency.

• A48 m/s
• B300 m/sCorrect
• C122.5 m/s
• D0.02 m/s

Use the universal wave equation v = f × λ. Here 120 × 2.5 = 300 m/s. The equation applies to every wave in physics, transverse or longitudinal.

• A40 s
• B0.4 s
• C0.025 sCorrect
• D2.5 s

Period and frequency are reciprocals: T = 1/f = 1/40 = 0.025 s. Each complete cycle takes twenty-five thousandths of a second.

• A2
• B4Correct
• C8
• DIt does not change

Energy is proportional to amplitude squared, so doubling the amplitude gives 2² = 4 times the energy. This is why a small rise in amplitude makes a sound noticeably louder.

• AMatter, which travels along with the wave
• BEnergy, while the medium stays in placeCorrect
• CBoth matter and energy in equal measure
• DNeither — a wave is only a pattern

Particles of the medium oscillate about a fixed rest position and return to it. A floating leaf bobs as ripples pass but does not travel to shore. Only energy — and the pattern carrying it — moves forward.

• AParallel to it
• BPerpendicular to itCorrect
• CIn a circle around it
• DIt does not move at all

Perpendicular motion is the defining feature. Shake a rope up and down and the wave runs along the rope while the rope itself only moves across the direction of travel.

• ALight
• BA wave on a guitar string
• CSound in airCorrect
• DA seismic S-wave

Sound is longitudinal — air molecules oscillate back and forth along the direction the sound travels. The other three all oscillate perpendicular to their travel.

• ATroughCorrect
• BCrest
• CRarefaction
• DNode

The highest point is the crest and the lowest is the trough. Rarefactions belong to longitudinal waves, and a node is a point of zero displacement on a standing wave.

• ALiquids are too dense
• BLiquids cannot resist shear, so there is no restoring forceCorrect
• CLiquids absorb all the wave's energy as heat
• DThey can — only gases block them

A transverse mechanical wave works by shearing the medium sideways, which needs the material to resist that shear and spring back. A liquid flows instead, so its shear modulus is zero and the wave speed √(G/ρ) collapses to zero.

• A16 m/s
• B126.5 m/sCorrect
• C256 m/s
• D16,000 m/s

Use v = √(T/μ) = √(64 / 0.004) = √16,000 ≈ 126.5 m/s. Tightening a string raises the tension and therefore the speed, which is how tuning a guitar works.

• ACrests
• BCompressionsCorrect
• CRarefactions
• DAntinodes

Compressions are the high-pressure, high-density regions; rarefactions are where the particles spread apart. Longitudinal waves have no crests or troughs at all.

• ASteel is denser, and denser materials always carry sound faster
• BSteel is far stiffer, and stiffness outweighs its greater densityCorrect
• CSteel is a better conductor of heat
• DSound waves become transverse inside solids

Speed depends on the ratio of stiffness to density, v = √(E/ρ). Steel is denser than air, which alone would slow sound down, but it is roughly a million times stiffer — and stiffness wins decisively.

• A331.3 m/s
• B343.0 m/s
• C349.5 m/sCorrect
• D361.6 m/s

v = 331.3 + 0.606 × 30 = 331.3 + 18.18 = 349.5 m/s. Every degree Celsius adds roughly 0.6 m/s, which is why sound carries differently on a hot day.

• ASound waves are too low in frequency
• BNo filter material is fine enough
• CSound oscillates along only one axis, so there is nothing to filter outCorrect
• DSound is already polarized when it leaves the source

Polarization works by admitting one direction of oscillation and blocking the rest. A longitudinal wave already vibrates in a single direction — along its own path — so a filter has nothing left to remove. The impossibility is structural, not technological.

• ASpace is too cold for molecules to vibrate
• BThere are too few particles to compress and rarefyCorrect
• CGravity is too weak to carry the wave
• DIt can, but far too quietly for us to hear

A longitudinal wave is a physical compression of matter. With almost no particles present there is nothing to squeeze together or spread apart, so the wave cannot exist. Light, being an oscillation of fields rather than matter, crosses a vacuum freely.

• AGamma, X-ray, ultraviolet, visible, infrared, microwave, radio
• BRadio, microwave, infrared, visible, ultraviolet, X-ray, gammaCorrect
• CRadio, infrared, microwave, visible, X-ray, ultraviolet, gamma
• DMicrowave, radio, infrared, visible, ultraviolet, gamma, X-ray

Radio waves have the longest wavelengths and gamma rays the shortest. Moving along that order, wavelength falls while frequency and photon energy both rise.

• ARadio waves
• BVisible light
• CMicrowaves
• DGamma raysCorrect

Photon energy is proportional to frequency (E = hf), and gamma rays have the highest frequency of any electromagnetic wave — above 30 exahertz. Radio waves, at the other end, carry the least.

• AMuch slower — longer waves move more slowly
• BMuch faster — longer waves move more quickly
• CExactly the same speedCorrect
• DIt depends on the amplitude of each

Every electromagnetic wave travels at c ≈ 299,792,458 m/s in a vacuum regardless of band. They differ in wavelength, frequency and energy — never in speed.

• ABetween radio waves and microwaves
• BBetween infrared and visible light
• CWithin the ultraviolet bandCorrect
• DBetween X-rays and gamma rays

The transition sits inside ultraviolet, at a photon energy of roughly 10 to 33 eV. UV's lower reaches merely cause sunburn; its upper reaches cross into genuinely cell-damaging territory, along with all X-rays and gamma rays.

• A380 to 700 nmCorrect
• B10 to 400 nm
• C700 nm to 1 mm
• D1 mm to 1 m

Human vision runs from about 380 nm at the violet end to 700 nm at the red end. Just beyond those limits lie ultraviolet (10–400 nm) and infrared (700 nm – 1 mm), both invisible to us.

• AP-waves are released first by the fault
• BP-wave speed depends on bulk modulus as well as shear modulusCorrect
• CS-waves take a longer route through the Earth
• DP-waves have a larger amplitude

Both leave at the same instant through the same rock. The longitudinal P-wave travels at √((K + 4G/3)/ρ) while the transverse S-wave travels at √(G/ρ). The P-wave formula contains everything the S-wave formula has plus the bulk modulus term, so it is always faster — typically by about 1.7× in rock.

• AThat the Earth is hollow
• BThat the Earth has a liquid outer coreCorrect
• CThat S-waves lose energy faster than P-waves
• DThat the crust is thicker than expected

Transverse S-waves cannot cross liquid, because a fluid has no shear rigidity. Their disappearance beyond about 103° could only mean a liquid layer deep inside. Oldham inferred a core from this in 1906; Lehmann found the solid inner core in 1936.

• APurely transverse
• BPurely longitudinal
• CBoth at once — the particles trace circlesCorrect
• DNeither, because water is not elastic

Surface waves combine both motions. Each water particle moves forward at the crest and backward in the trough while also rising and falling, tracing a near-circular orbit that shrinks rapidly with depth. Seismic Rayleigh waves do the same in rock.

• AIt travels at a finite speed
• BIt can be polarizedCorrect
• CIt reflects off mirrors
• DIt can be split into colours by a prism

Only a transverse wave has a plane of oscillation directions for a filter to select from. Reflection, refraction and a finite speed are shared by both wave types, but polarization is possible only for transverse waves — which is what settled the argument in the early 1800s.

• ABoth can be polarized
• BBoth require a material medium
• CBoth obey v = fλ and carry energy proportional to amplitude squaredCorrect
• DBoth produce compressions and rarefactions

They share far more than they differ by: the same wave equation, v = fλ, T = 1/f, E ∝ A², and every wave behaviour including reflection, refraction, diffraction and interference. Only transverse waves polarize, only longitudinal waves always need a medium, and only longitudinal waves form compressions.