Waves and tides

Correct answer: B. Wave period

The governing wave relationships are period, wavelength, and speed. Wave period is the time interval between the passage of successive crests at a fixed point, whereas wavelength is the distance between successive crests at a given instant. The question says the time interval increases, so the period has changed. It separately says the crest-to-crest distance remains constant, so wavelength has not changed. Since wave speed is expressed as c = wavelength divided by period, a constant wavelength with a larger period would imply a lower propagation speed, if the wave is treated under the same simple conditions. Therefore B is correct; A describes distance, while C and D are unrelated.

Correct answer: D. The wave can steepen and break

As a wave enters shallow water, it slows and its wavelength shortens. Its height relative to the water depth can increase, making the wave steeper. If the crest becomes unstable, it topples forward and breaks. A tide is a different phenomenon, caused mainly by the gravitational effects of the Moon and Sun.

Correct answer: A. Wave angle can affect the direction of sediment transport

Waves approaching the shore at an angle move sediment up the beach obliquely; backwash generally carries it back downslope more directly. This creates net longshore sediment transport. A change in wave approach angle can change the direction or strength of that transport, affecting how a sand strip or spit grows. Thus A is correct.

Correct answer: B. The Sun's and Moon's tidal effects reinforce one another

At new moon, the Sun, Moon, and Earth are approximately aligned. The Sun's and Moon's tidal effects then reinforce one another, producing a spring tide with a larger-than-average tidal range. Calm wind makes wind-generated waves an unlikely explanation. Therefore B is correct.

Correct answer: D. A spring tide increased the available depth at high tide

Near full moon, the Sun, Earth, and Moon are approximately aligned, producing a spring tide with a larger tidal range. At high tide, the increased water depth can provide more under-keel clearance for a vessel in a shallow port channel, making entry easier. Thus D is correct.

Correct answer: B. Sediment transport by tide-driven horizontal water flow

A tidal current is the horizontal flow of water associated with the rise and fall of the tide. If it is strong enough, it can keep fine particles such as silt or clay suspended and carry them out of the bay. This is sediment transport by a tidal current, so B is correct.

Correct answer: C. Large tidal range of spring tide

The governing concept is the relationship between lunar phase and tidal range. At the first- or third-quarter Moon, the Sun and Moon exert their tidal forces in approximately perpendicular directions. These forces partly offset one another, producing a neap tide, whose tidal range is relatively small. Therefore, options A, B and D describe the third-quarter situation consistently. Option C is wrong because a large tidal range belongs to a spring tide, which normally occurs near the new Moon and full Moon when the Sun, Earth and Moon are approximately aligned. The question asks for the incorrect statement, so C is the unambiguous answer.

Correct answer: A. Waves have been confused with the definition of tides

The governing distinction is between waves and tides. Ordinary surface waves are mainly generated by wind and represent the transfer of energy through water; individual water particles usually move in orbital or oscillatory paths rather than travelling across the ocean with the wave form. In contrast, tides are the periodic rise and fall of sea level caused primarily by the gravitational attraction of the Moon and the Sun, together with Earth’s rotation. Thus the quoted definition describes tides, not waves. Option A correctly identifies the error. Options B and C are valid associations with waves, while option D may describe where waves act but is not the definitional mistake.

Correct answer: A. The new Moon generally produces a spring tide

The governing concept is the alignment of the Sun, Earth and Moon. Around the new Moon, the Sun and Moon lie in nearly the same direction as viewed from Earth. Their gravitational tide-producing forces therefore reinforce one another, creating a spring tide with a comparatively large tidal range. A similar spring tide occurs around the full Moon, when the Sun and Moon are on opposite sides of Earth. Neap tides occur instead near the first and third quarters, when the two forces act at approximately right angles and partly counteract each other. Option A is correct. The other options are wrong because tides still occur at new Moon, neap tides are not caused only by wind, and a neap tide is not a tsunami.

Correct answer: C. Spring tides at full and new moon, neap tides at the quarter phases

The governing concept is the alignment of the Sun, Moon, and Earth and its effect on the tidal range. At new moon and full moon, the Sun and Moon exert their tidal forces along nearly the same line. Their effects therefore reinforce one another, producing spring tides with a comparatively large range between high and low water. At the first-quarter and third-quarter phases, the Sun and Moon are approximately at right angles as viewed from Earth. Their tidal effects partly oppose one another, producing neap tides with a smaller range. Thus option C correctly pairs the two syzygy phases with spring tides and the quarter phases with neap tides. Option A reverses both relationships, option B also reverses them, and option D ignores the regular lunar control of tides.

Correct answer: A. Sediment sorting and deposition by waves

The governing geomorphic concept is the depositional and sorting work of wave action. Breaking waves lose or redistribute energy as they enter shallow water and interact with the shore. Their changing competence means that particles are not carried equally: coarser or heavier grains require stronger movement, whereas finer grains can remain suspended or be transported farther under suitable conditions. As energy varies across the beach and swash zone, sediments may become sorted by size, shape, or density and then deposited in different positions. Option A correctly names both relevant processes: sorting and deposition by waves. Option B concerns molten material from a volcano, C is an astronomical event, and D concerns river development; none explains size-wise arrangement of coastal sediment by breaking waves.

Correct answer: A. Because regular rise and fall make energy generation predictable

Tidal-energy generation uses the predictable movement associated with the rise and fall of sea level, often through a barrage, lagoon, or tidal-stream turbine. A large tidal range provides a substantial difference in water level or a strong tidal flow, which increases the possible energy per cycle. Regularity is equally important because the generating system must know when water will move and must receive repeated cycles to produce dependable electricity. Predictable timing supports grid planning, maintenance, storage decisions, and efficient operation, even though tidal output is not constant at every moment. Option A correctly explains why both amplitude and regular recurrence matter. Options B, C, and D are unnecessary or impossible conditions and do not describe the physical or operational basis of tidal power.

Correct answer: B. Wave period

The governing concept is the distinction between wavelength and wave period. Wavelength is the horizontal distance between two successive crests or troughs, whereas wave period is the time interval between their successive passages at a fixed point. Therefore, when the clue supplies time rather than distance, the required property is the wave period, making option B correct. Wavelength would be appropriate only if the question referred to separation in metres. Tidal range concerns the difference between high and low tide, and sediment budget concerns sediment gains, losses, and transfers; neither describes the timing of crests.

Correct answer: A. It is not a season, but a large tidal range caused by near alignment of the Sun and Moon

The governing concept is the lunar phase and tidal range, not the seasons. During a new moon or full moon, the Sun, Earth, and Moon are approximately aligned. Their gravitational effects reinforce one another, producing higher high tides and lower low tides; the difference between them, called tidal range, becomes relatively large. Thus option A is correct. The word “spring” refers to the tide’s tendency to rise or spring strongly, not to the spring season. A storm wave is generated by atmospheric disturbance, while an undersea earthquake may generate a tsunami; neither is a spring tide.

Correct answer: A. Waves can perform both erosional and depositional geomorphic work

The governing concept is the dual geomorphic work of waves. Breaking waves release hydraulic pressure and abrasion against cliffs, joints, and other weaknesses, so they can erode and transport rock fragments. When wave energy or current velocity decreases, the transported load may be deposited on beaches, bars, spits, or other nearby features. Therefore option A is correct: the same coastal system can experience erosion at one location and deposition at another, or at different times. Waves do not create tides, they clearly interact with coasts, and no sediment comes from the Moon.

Correct answer: D. Bottom friction increases, lower part slows, wave becomes unstable

The governing concept is shallow-water wave transformation. As a wave enters water whose depth is small compared with its wavelength, interaction with the seabed increases. Friction and drag slow the lower part of the orbital motion first, while the upper part continues moving relatively faster. The wavelength shortens, the wave height becomes greater in proportion to depth, and the crest becomes increasingly steep. Once the wave becomes unstable, the crest topples forward and the wave breaks, releasing energy through turbulence and spray. Therefore option D gives the correct sequence. The other choices describe unrelated or physically impossible events: calm wind does not itself create a tide, sea colour does not freeze a wave, and the Moon stopping or hiding is not the immediate mechanism of surf breaking.

Correct answer: A. Sediment can be progressively transported parallel to the coast

The governing concept is longshore sediment transport. When waves approach the shoreline obliquely, their breaking swash moves water and loose particles up the beach at an angle. Backwash then returns downslope under gravity, usually more directly seaward. Repetition of this angled uprush and return produces a zigzag movement whose net result is transport parallel to the coast. The direction depends on the angle from which the waves arrive, the beach slope, and local currents, so the option appropriately says sediment can be moved progressively rather than claiming an absolute direction. Option A is correct. The other alternatives are scientifically unrelated: sediment does not normally vaporise, tides do not permanently stop, and gravity remains essential to beach sediment movement.

Correct answer: B. Nearly aligned position of Sun, Earth and Moon

The governing concept is the spring tide. At full moon, the Earth lies approximately between the Sun and Moon, so the gravitational pulls of the Sun and Moon act along nearly the same line. Their effects reinforce one another, increasing the difference between high-water and low-water levels; this difference is the tidal range. Calm wind is important in the question because it removes wind-generated waves as the main explanation. Thus option B is correct. A spring tide does not mean that tides occur only because of wind, sea colour, or sand supply. It is a periodic astronomical effect, although the exact observed range is also modified by coastline shape, basin depth, and local ocean conditions.

Correct answer: C. Because Sun and Moon effects partly reduce at right angles

The governing concept is the neap tide and its reduced tidal range. Near the first- and third-quarter Moon, the Sun, Earth, and Moon form an approximately right angle. The solar and lunar tidal-producing forces then do not reinforce one another along the same line; their effects partly offset, producing a smaller difference between high tide and low tide. Since tidal current is the horizontal movement of water associated with changing tidal levels, a smaller range generally provides a weaker driving gradient and can produce weaker flow, although local bay shape may modify it. Option C is correct. Wind stopping, absence of seawater, or permanent loss of lunar gravity is not the cause.

Correct answer: B. Tidal current

The governing concept is a tidal current, which is the horizontal movement of seawater produced by the periodic rise and fall of the tide. In a narrow bay, the restricted opening and confined shape can concentrate or accelerate the exchange of water during flood tide, when water moves inward, and ebb tide, when it moves outward. The description concerns directional water transport, not merely the up-and-down orbital motion of a normal wave. Therefore option B is correct. Tsunami deposition would require a tsunami event and would describe sediment left behind after unusual inundation, not the regular in-and-out flow. Sea-colour change has no causal role, and the current is not simply a wind wave.

Correct answer: A. Erosion can be faster on the weak rocky coast

The governing concept is differential resistance to coastal erosion. Equal wave energy does not guarantee equal erosion because rocks differ in hardness, strength, jointing, porosity, weathering, and resistance to hydraulic action and abrasion. A weak, fractured, or poorly cemented coast can be worn back more rapidly as waves compress air in cracks, remove loosened particles, and abrade the surface. A hard, massive rock coast may resist the same impacts for a longer period, although it can still erode gradually. Thus option A is correct: the weak rocky coast can experience faster erosion. The other options are invalid because erosion is not automatically zero, hard rock does not instantly melt, and rock properties are central to the comparison.

Correct answer: A. Wave energy can increase because the wind acts over a longer stretch of water.

Option A is correct. Fetch is the distance over which wind blows across the water without a major obstruction. With wind speed and other conditions broadly similar, a longer fetch gives the wind more distance to transfer energy to the water, so waves can become larger and more energetic. Wind duration and local conditions also matter. Tides, by contrast, are mainly caused by the gravitational effects of the Moon and Sun.

Correct answer: B. The combined gravitational effects of the aligned Sun and Moon

At new moon, the Sun, Moon and Earth are approximately aligned. Their tidal effects reinforce one another, producing a spring tide with a larger tidal range than a neap tide. The shape of a bay can modify the local height and timing of tides, but it does not replace this astronomical cause. Therefore, option B is correct.

Correct answer: C. It indicates substantial wave energy and a greater potential for coastal impact

Wave height is the vertical distance from crest to trough, and wave period is the time between successive crests passing a fixed point. A high wave with a long period can carry substantial energy and may affect the coast strongly. The actual impact also depends on factors such as wave direction and nearshore conditions. Thus option C is the best interpretation; the wave properties alone do not identify a neap tide.

Correct answer: D. First quarter is associated with a neap tide

First quarter is one of the lunar phases associated with neap tides: the Sun and Moon act at approximately right angles, so their tidal effects partly offset one another. Local coastal shape can strengthen a current in a particular place, but that does not change the astronomical tide classification. Therefore, option D is correct.