🌊 Chapter 12: Waves – Short Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This chapter covers wave motion, transverse & longitudinal waves, reflection, refraction, diffraction, seismic waves, tsunamis, wave equation. Each short question includes the exact exam-ready answer as per official PECTAA 2026 Physics curriculum.
📚 Related Resources – Chapter 12: Waves
Waves chapter covers mechanical and electromagnetic waves, wave characteristics, and real-life wave phenomena.
📖 Short Questions & Answers (PECTAA 2026)
1. Define wave motion.
Wave motion is a process by which energy is transferred from one point to another without the physical transfer of matter.
Wave motion is a process by which energy is transferred from one point to another without the physical transfer of matter.
2. How do waves transfer energy?
Waves transfer energy through vibrations or oscillations of the medium's particles or through oscillating electric and magnetic fields. For example, when a twig is dropped into still water, ripples spread across the surface carrying energy outward, yet the water and the twig remain mostly in place.
Waves transfer energy through vibrations or oscillations of the medium's particles or through oscillating electric and magnetic fields. For example, when a twig is dropped into still water, ripples spread across the surface carrying energy outward, yet the water and the twig remain mostly in place.
3. What are the two main types of waves?
(i) Mechanical Waves: require a medium (e.g., sound, water waves). (ii) Electromagnetic Waves: do not require a medium (e.g., light, radio waves, X-rays).
(i) Mechanical Waves: require a medium (e.g., sound, water waves). (ii) Electromagnetic Waves: do not require a medium (e.g., light, radio waves, X-rays).
4. What is the speed of electromagnetic waves in vacuum and what is the electromagnetic spectrum?
All electromagnetic waves travel in vacuum at \(3 \times 10^8 \, \text{ms}^{-1}\) (speed of light). The complete range of these waves is called the electromagnetic spectrum.
All electromagnetic waves travel in vacuum at \(3 \times 10^8 \, \text{ms}^{-1}\) (speed of light). The complete range of these waves is called the electromagnetic spectrum.
5. What are the main types of mechanical waves?
Transverse waves: particles vibrate at right angles to wave direction (e.g., water waves, light). Longitudinal waves: particles vibrate parallel to wave direction (e.g., sound waves).
Transverse waves: particles vibrate at right angles to wave direction (e.g., water waves, light). Longitudinal waves: particles vibrate parallel to wave direction (e.g., sound waves).
6. Define crest and trough.
Crest: The region of a transverse wave above the mean position (upper part). Trough: The region below the mean position (lower part).
Crest: The region of a transverse wave above the mean position (upper part). Trough: The region below the mean position (lower part).
7. Define compression and rarefaction.
Compression: region where particles are close together (high pressure). Rarefaction: region where particles are spread apart (low pressure).
Compression: region where particles are close together (high pressure). Rarefaction: region where particles are spread apart (low pressure).
8. Define amplitude of a wave.
Amplitude is the maximum displacement of a point on the wave from its undisturbed (rest) position. It indicates the energy carried by the wave.
Amplitude is the maximum displacement of a point on the wave from its undisturbed (rest) position. It indicates the energy carried by the wave.
9. Define wavelength \((\lambda)\).
The distance between two corresponding points on adjacent waves (crest to crest or compression to compression). SI unit: metre (m).
The distance between two corresponding points on adjacent waves (crest to crest or compression to compression). SI unit: metre (m).
10. Define frequency \((f)\).
The number of complete wave cycles that pass a fixed point in one second. Measured in hertz (Hz).
The number of complete wave cycles that pass a fixed point in one second. Measured in hertz (Hz).
11. Define Time Period \((T)\).
Time required for one complete wave to pass a fixed point; \(T = 1/f\). Measured in seconds (s).
Time required for one complete wave to pass a fixed point; \(T = 1/f\). Measured in seconds (s).
12. Define wave front.
An imaginary surface on which all points have the same phase of vibration (same displacement and direction).
An imaginary surface on which all points have the same phase of vibration (same displacement and direction).
13. Two waves travel at the same speed, but one has a higher frequency. Which has the shorter wavelength?
The wave with higher frequency has the shorter wavelength because \(\nu = f\lambda\) (speed constant).
The wave with higher frequency has the shorter wavelength because \(\nu = f\lambda\) (speed constant).
14. Prove that \(\nu = f\lambda\) (Wave Equation).
Wave speed = distance/time. In one period T, wave travels one wavelength \(\lambda\): \(\nu = \lambda / T\). Since \(T = 1/f\), \(\nu = f\lambda\).
Wave speed = distance/time. In one period T, wave travels one wavelength \(\lambda\): \(\nu = \lambda / T\). Since \(T = 1/f\), \(\nu = f\lambda\).
15. Define reflection of waves.
Reflection is the bouncing back of waves into the same medium after striking the surface of another medium.
Reflection is the bouncing back of waves into the same medium after striking the surface of another medium.
16. State the law of reflection.
Angle of incidence = Angle of reflection.
Angle of incidence = Angle of reflection.
17. Define refraction of waves.
When a wave passes from one medium into another at an angle, its wavelength and speed change, causing the wave to bend. This is called refraction.
When a wave passes from one medium into another at an angle, its wavelength and speed change, causing the wave to bend. This is called refraction.
18. Define diffraction of waves.
The spreading of waves when they pass through a slit or move around an obstacle is called diffraction.
The spreading of waves when they pass through a slit or move around an obstacle is called diffraction.
19. What are seismic waves?
Seismic waves are waves that pass through the Earth, typically created by earthquakes, volcanic eruptions, or explosions.
Seismic waves are waves that pass through the Earth, typically created by earthquakes, volcanic eruptions, or explosions.
20. What are Primary Waves (P-Waves)?
Fastest seismic waves, first detected during an earthquake. They travel through solids, liquids, and gases via compressions and expansions in the same direction as wave travel.
Fastest seismic waves, first detected during an earthquake. They travel through solids, liquids, and gases via compressions and expansions in the same direction as wave travel.
21. What causes a tsunami in the ocean?
Tsunamis are caused by sudden disturbances under the sea such as underwater earthquakes, volcanic eruptions, or landslides.
Tsunamis are caused by sudden disturbances under the sea such as underwater earthquakes, volcanic eruptions, or landslides.
22. If waves do not carry matter, how does a tsunami destroy buildings?
A tsunami carries a huge amount of energy. When it reaches shore, speed decreases and height increases, producing a powerful force that damages buildings.
A tsunami carries a huge amount of energy. When it reaches shore, speed decreases and height increases, producing a powerful force that damages buildings.
23. Why does a tsunami become more dangerous as it approaches the shore?
Out at sea, a tsunami may be only 1m high. As it nears shore, deceleration from ~250 m/s to ~15 m/s causes wavelength to shorten and height to increase dramatically, creating destructive walls of water.
Out at sea, a tsunami may be only 1m high. As it nears shore, deceleration from ~250 m/s to ~15 m/s causes wavelength to shorten and height to increase dramatically, creating destructive walls of water.
📐 Key Formulas – Waves
Wave Equation: \( \nu = f \lambda \)
Time Period: \( T = \frac{1}{f} \)
💡 Exam Tip:
For board exams, define key wave properties precisely, state wave equation with derivation, and relate to real-life examples like tsunamis and seismic waves. These questions follow PECTAA 2026 pattern by Muhammad Tayyab.
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus