Key Concepts and Worked Examples in Oscillations and Waves
FAQs on Oscillations and Waves Practice Paper
1. What is the difference between oscillation and wave?
Oscillation refers to the repetitive back-and-forth motion of a particle or object around a mean position, while a wave is a disturbance that transfers energy through space or a medium without transferring matter.
Key differences:
- Oscillation is local motion (of an object/particle), while wave is the propagation of oscillations through space.
- Oscillations can exist without waves, but waves are usually made up of many oscillating particles.
- Examples: Pendulum motion (oscillation), sound wave (travelling wave).
2. What are the types of oscillations in physics?
Oscillations in physics can be classified based on their nature and external influence:
- Free Oscillations: System oscillates without external force after initial displacement.
- Damped Oscillations: Amplitude decreases over time due to resistive force (like friction).
- Forced Oscillations: External periodic force drives the system.
- Resonant Oscillations: Amplitude increases due to matching of natural and external frequency.
3. What is simple harmonic motion (SHM)?
Simple harmonic motion (SHM) is a type of periodic oscillation where the restoring force is directly proportional to the displacement and acts towards the mean position.
Main points:
- The motion is sinusoidal (follows a sine/cosine function).
- Examples: Mass-spring system, simple pendulum (for small angles).
- Keywords: Amplitude, time period, frequency, phase.
4. What is the equation of a wave?
The standard equation of a travelling wave is:
y(x, t) = A sin(kx - ωt + φ), where:
- A = Amplitude
- k = Wave number (2π/λ)
- ω = Angular frequency (2πf)
- φ = Initial phase
- λ = Wavelength
- f = Frequency
5. How do you distinguish between longitudinal and transverse waves?
Longitudinal and transverse waves differ based on the direction of particle vibration relative to the direction of wave propagation:
- Longitudinal waves: Particles vibrate parallel to the direction of wave (e.g., sound wave).
- Transverse waves: Particles vibrate perpendicular to the direction of wave (e.g., light wave, waves on string).
6. What are the characteristics of waves?
Waves have several important characteristics:
- Wavelength (λ): Distance between two consecutive crests/troughs.
- Frequency (f): Number of oscillations per second.
- Amplitude (A): Maximum displacement from mean position.
- Velocity (v): Speed of wave propagation; v = fλ.
- Phase: Describes the relative position within one cycle.
7. What is resonance in oscillatory motion?
Resonance occurs when the frequency of an external force matches the natural frequency of a system, resulting in maximum amplitude of oscillation.
Key points:
- Common in musical instruments and bridges.
- At resonance, energy transfer is highly efficient.
- Example: Swing gets higher when pushed at correct regular intervals.
8. What is the difference between damped and undamped oscillations?
Undamped oscillations occur without energy loss, so amplitude stays constant. Damped oscillations lose energy (due to friction or air resistance), so amplitude decreases over time.
Differences:
- Undamped: Ideal case, never stop.
- Damped: Real case; system gradually comes to rest.
9. What is the principle of superposition of waves?
The superposition principle states that when two or more waves meet at a point, the total displacement at that point is equal to the sum of the individual displacements.
- Causes constructive and destructive interference.
- Applicable to all linear waves (sound, light, water waves).
10. Explain the difference between mechanical and electromagnetic waves.
The main difference is based on the medium of propagation:
- Mechanical waves require a material medium (e.g., sound, water waves).
- Electromagnetic waves do not need a medium and can travel through vacuum (e.g., light, radio waves).
11. What is meant by time period and frequency in oscillations?
The time period (T) is the time taken for one complete oscillation, while frequency (f) is the number of oscillations per second. They are related by:
f = 1/T
- Time period: measured in seconds (s)
- Frequency: measured in hertz (Hz)
12. What factors affect the frequency of a simple pendulum?
The frequency of a simple pendulum depends on its length (l) and the acceleration due to gravity (g):
- f = (1/2π) × √(g/l)
- Longer pendulum: lower frequency
- Heavier bob or larger amplitude does not affect frequency (for small angles)






















