What this covers
This standard sits within Waves. In a one-to-one lesson we make sure the idea is clear first, then move straight to applying it in the exact way SPM asks, with correct units and full working.
Formulas you may need
How it is examined
It can appear in Paper 1 (objective) and Paper 2 (structured), and where an experiment applies, in Paper 3. We do not predict which questions appear; we prepare the technique for all of them.
A common mistake
How to study it
Learn the definition precisely, practise one or two SPM-style questions with full working, and link it to the rest of Waves. If it keeps costing marks, a one-to-one lesson fixes exactly that.
Waves · Formulas · Exam Papers
What you need to know
A wave transfers energy from one point to another without transferring matter, and every wave can be classified as transverse or longitudinal. In a transverse wave, particles of the medium vibrate perpendicular to the direction the wave travels, forming crests and troughs; examples include water waves and light waves.
In a longitudinal wave, particles vibrate parallel to the direction of travel, forming compressions and rarefactions; sound waves are the main example. Several quantities describe a wave.
Amplitude is the maximum displacement of a particle from its rest position, measured in metres (m). Wavelength, symbol λ, is the distance between two successive points that are in phase, such as crest to crest, measured in metres (m).
Period T is the time taken for one complete oscillation, in seconds (s), while frequency f is the number of complete oscillations per second, measured in hertz (Hz), where f = 1/T. A wavefront joins points on a wave that are in phase. The wave equation v = fλ connects speed (m s⁻¹), frequency (Hz) and wavelength (m), and must be memorised for calculations.
Worked example
A water wave in a ripple tank has a frequency of 5 Hz and a wavelength of 0.04 m. Using the wave equation v = fλ, the speed of the wave is calculated as v = 5 Hz × 0.04 m = 0.2 m s⁻¹.
This shows how the three quantities are linked: if the frequency of the vibrating dipper increases while the wavelength stays fixed, the wave speed increases proportionally. Conversely, the period of this wave can be found from T = 1/f = 1/5 Hz = 0.2 s, meaning each complete oscillation takes 0.2 s.
Students should present such calculations with the formula stated first, correct substitution of values with units shown, and the final answer rounded appropriately with the correct unit. A common extension is to sketch a displacement-distance graph to identify amplitude and wavelength, or a displacement-time graph to identify amplitude and period, since confusing these two graphs is a frequent source of error.
Always label axes with quantity and unit, for example distance / m or time / s, and read values directly off the graph carefully.
How it is examined
In Paper 1, objective questions often test definitions and require you to identify whether a wave is transverse or longitudinal from a diagram, or to calculate v, f or λ using v = fλ. In Paper 2, structured questions typically give a displacement-distance or displacement-time graph and ask you to state the amplitude, determine the wavelength or period, and calculate frequency or speed, with command words such as "define", "state" and "calculate" requiring different levels of detail.
"Define" needs a precise one-sentence statement, while "calculate" requires working shown with correct units at every step. In Paper 3, practical work may involve using a ripple tank or a slinky spring to measure wavelength and estimate wave speed, so recording apparatus, tabulating readings and describing the method clearly are assessed.
A common mistake is mixing up crest-to-crest with crest-to-trough when measuring wavelength, or forgetting to convert units such as centimetres to metres before substituting into a formula, which leads to answers that are out by a factor of ten or more.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)