Q: What does IP Physics Notes (Upper Secondary, Year 3-4): 8) Waves cover? A: Review EM spectrum properties, mechanical wave terms, sound/ultrasound, and CRO measurements for IP Year 3-4.
Quick recap -- Waves transport energy without carrying matter. Understand the language (wavelength, frequency, period), track phase with wavefronts, and apply the same maths from microwaves to ultrasound echoes.
The core idea is simple: Waves transfer energy without transferring matter overall.
Use it as a working check: Know wavelength, frequency, period, amplitude, and speed. Frequency stays fixed when waves cross a boundary, while speed and wavelength can change.
Then go one layer deeper: Use the EM spectrum, sound, ultrasound, and CRO sections to practise matching a wave type to its equation, graph reading, use, and hazard.
Keep your practice loop tight via our IP Physics tuition hub-it links each topic here to quizzes, diagnostics, and WA-style problem sets.
For Integrated Programme students: Your current school materials, teacher instructions, and assessment scope take precedence because IP topic sequence and depth vary by school. This is an Eclat IP guide, not the O-Level / SEC G3 exam-track guide.
Marcus Pang combines wave motion, sound, and the Electromagnetic Spectrum because IP questions often require students to use the ideas together rather than as isolated topics.
Eclat extension depth: plane-wave refraction analysis and cathode-ray oscilloscope measurement remain in the main Eclat route even though the current K323 Topics 10 and 11 do not name CRO operation.
2027 national comparison: this one Eclat chapter overlaps with both K323 Topic 10, General Properties of Waves including Sound, and Topic 11, Electromagnetic Spectrum.
Check your school: follow the current task's expectations for graph depth, CRO settings, and application examples.
Gamma: cancer therapy, sterilising equipment; highly penetrating.
Entering a medium changes wave speed and wavelength but leaves frequency constant.
EM Spectrum Comparison Checkpoint
When a question gives two EM waves, compare the linked quantities in one direction before naming the use or hazard.
Situation
What changes together
How to use it in answers
Common trap
Moving from radio toward gamma
Wavelength decreases, while frequency and photon energy increase.
Higher-frequency EM waves are more likely to be ionising and need stricter shielding.
Saying gamma travels faster than radio in vacuum.
Entering glass, water, or another medium
Speed and wavelength change; frequency stays the same.
Use the unchanged frequency with the new speed to reason about the new wavelength.
Changing frequency to explain refraction.
Choosing a use
Match the property to the task: heating, imaging, communication, sterilisation, or therapy.
Name the property, then the application, such as penetration for X-ray imaging.
Listing a use without linking it to absorption or penetration.
Comparing hazards
Higher-frequency ultraviolet, X-ray, and gamma radiation can damage cells because their photons carry more energy.
Mention exposure control, shielding, or limiting dose when the question asks about safety.
Treating visible light and ultraviolet as the same hazard.
Worked check - halving wavelength
In vacuum, one EM wave has half the wavelength of another. Since c=fλ and c is unchanged in vacuum, halving λ doubles f. The wave has higher photon energy, but it still travels at c in vacuum.
Misconception check: the EM spectrum order is not a speed ranking. In vacuum, all EM waves travel at the same speed; the order is about frequency and wavelength.
Wave Terminology & Equation
Wavelengthλ: distance between successive points in phase.
Frequencyf: oscillations per second (Hz).
PeriodT=f1.
Amplitude: maximum displacement.
Wavefront: locus of points in phase.
Wave speed: v=fλ
Displacement-time graphs show period; displacement-distance graphs show wavelength.
Wave graph reading checkpoint
Before using v=fλ, identify what the horizontal axis measures. The same wave shape can show either time or distance, so the spacing between crests does not always mean wavelength.
Graph shown
Horizontal spacing between matching crests gives
Next calculation
Common trap
Displacement-time graph
Period T
Find frequency using f=1/T.
Calling the crest spacing wavelength just because the graph looks like a wave.
Displacement-distance graph
Wavelength λ
Use v=fλ if frequency is known.
Using 1/λ as the frequency.
CRO trace
Period from horizontal divisions times time-base
Convert milliseconds to seconds, then use f=1/T.
Treating divisions as seconds without applying the time-base.
Worked check: if a displacement-time graph shows one full cycle taking 0.020s, then T=0.020s and f=1/T=50Hz. If a separate displacement-distance graph for the same wave shows crest spacing 6.8m, then λ=6.8m and v=50×6.8=340m⋅s−1.
Misconception check: period is a time interval; wavelength is a distance. They are linked by wave speed, but they are read from different graph axes.
Transverse vs Longitudinal Waves
Transverse: oscillation is perpendicular to wave travel, as for EM waves and waves on strings.
Longitudinal: oscillation is parallel to wave travel, as for sound and compression waves.
Demonstrate via slinkies or ripple tanks; circular and plane waves obey the same rules.
Particle motion direction checkpoint
For wave-type questions, separate the direction the wave travels from the direction each particle or field oscillates. The particles do not travel all the way with the wave; they vibrate around their positions while energy moves through the medium.
Wave type
Oscillation direction
Wave travel direction
Example
Common trap
Transverse mechanical wave
Perpendicular to travel
Along the rope, surface, or wavefront direction
A rope wave moving right while the rope moves up and down
Saying the rope particles move right with the wave.
Longitudinal mechanical wave
Parallel to travel
Along the line of compressions and rarefactions
Sound travelling right while air particles vibrate left and right
Drawing crests and troughs instead of compressions and rarefactions.
Electromagnetic wave
Field oscillations are perpendicular to travel
Direction of energy transfer
Light travelling forward without needing air particles
Calling EM waves longitudinal because they can travel through space.
Worked check: in a sound wave travelling from a speaker to a wall, the sound energy moves toward the wall, but each air particle vibrates back and forth about its own position. In a rope wave travelling to the right, the rope elements may move up and down while the disturbance moves right.
Misconception check: "wave direction" and "particle vibration direction" answer different questions. Use both directions before deciding whether the wave is transverse or longitudinal.
Reflection & Refraction of Wavefronts
Plane water waves reflect with i=r just like light.
Crossing boundaries alters speed, so wavelength changes while frequency remains fixed.
Waves bend toward the normal when slowing down, away when speeding up.
Boundary-change direction checkpoint
When a wave crosses into a new medium, decide the speed change before drawing the bend. Frequency is set by the source, so the wave adjusts its wavelength and direction instead.
Boundary change
Speed in new medium
Wavelength in new medium
Direction of refraction
Common trap
Enters a slower medium
Decreases.
Decreases because λ=v/f and f is unchanged.
Bends toward the normal.
Saying the frequency decreases to fit the shorter wavelength.
Enters a faster medium
Increases.
Increases because λ=v/f and f is unchanged.
Bends away from the normal.
Drawing the bend correctly but explaining it using a changing frequency.
Hits a straight barrier and reflects
Speed stays the same in the same medium.
Wavelength stays the same in the same medium.
Angle of incidence equals angle of reflection.
Measuring the angles from the surface instead of from the normal.
Worked check: if water waves enter a shallower region and slow down, the wavefront spacing decreases. The refracted wave bends toward the normal because the part of the wavefront that reaches the shallow region first slows first.
Misconception check: refraction is not caused by the source changing its rhythm. The source frequency remains fixed; the medium changes the wave speed.
Sound Waves
Sound is produced by a vibrating source and requires a material medium for transmission.
It travels as longitudinal compressions and rarefactions; typical speed in air ≈330m⋅s−1 at room temperature.
Greater amplitude is heard as greater loudness, while greater frequency is heard as higher pitch.
Hearing range: 20Hz≤f≤20kHz.
Echo rangefinding: s=21vt (half because of the out-and-back path).
Reflections arise at boundaries with different acoustic impedances.
Cathode Ray Oscilloscope (CRO)
Microphone converts sound to voltage; CRO displays voltage vs time.
Y-gain sets volts per division; time-base sets seconds per division.
Peak voltage = (vertical divisions) x (Y-gain).
Period = (horizontal divisions) x (time-base); frequency f=T1.
CRO Reading Checkpoint
Before calculating, decide whether you are reading a vertical size or a horizontal size.
What the question asks for
Read from the screen
Multiply by
Finish with
Peak voltage
Centre line to crest in vertical divisions
Y-gain
Report voltage.
Peak-to-peak voltage
Trough to crest in vertical divisions
Y-gain
Divide by 2 only if the question asks for peak voltage.
Period
One full cycle in horizontal divisions
Time-base
Use f=1/T for frequency.
Misconception check: do not use the time-base for amplitude or the Y-gain for period. The vertical scale measures voltage; the horizontal scale measures time.
Worked example - CRO frequency
A sound trace takes 4 horizontal divisions for one complete cycle. The time-base is 0.50ms per division.
Period: T=4×0.50ms=2.0ms=0.0020s.
Frequency: f=1/T=1/(2.0×10−3)=500Hz.
Common trap: using the 4 divisions directly as T=4s. Divisions are not seconds until you multiply by the time-base.
Worked Example: Determining Sound Speed
A hall echo returns 0.25s after a clap. With sound speed 343m⋅s−1, the wall is at
s=21vt=21×343m⋅s−1×0.25s≈42.9m.
Practice Quiz
Test wave vocab, echo timing, interference ideas, and EM spectrum recall with these mixed-format questions.
Key Takeaways
Waves move energy, not matter; use v=fλ to connect frequency and wavelength.
Boundary changes keep frequency fixed but adjust speed and direction.
Ultrasound timing always divides by two for the round trip.
CRO measurements translate sound questions into voltage and time scales.
