Standing waves and resonance are fundamental concepts in wave mechanics and form an important part of the physics syllabus for NEET, JEE, and CUET examinations. These standing waves and resonance topics explain how waves behave when confined within a medium and how systems respond strongly to specific frequencies. A clear conceptual understanding of these standing waves and resonance ideas   is essential for solving both theoretical and numerical problems related to sound waves, strings, pipes, and resonance devices.

A standing wave, also known as a stationary wave, is formed when two waves of the same frequency, wavelength, and amplitude travel in opposite directions through a medium and interfere with each other. Unlike progressive waves, standing waves do not transfer energy from one point to another. Instead, they create fixed patterns of oscillation characterized by nodes and antinodes. Nodes are points where the displacement of particles is always zero, while antinodes are points where the displacement is maximum. The distance between two consecutive nodes or antinodes is equal to λ/2, a relation frequently used in numerical questions.

Standing waves are commonly observed in stretched strings, air columns in pipes, and resonance tubes. These systems help explain musical sounds and the working principles of instruments like guitars, flutes, and organ pipes. In competitive exams, questions often test the relationship between wavelength, frequency, length of the medium, and boundary conditions (fixed or open ends).

Closely related to standing waves is the phenomenon of resonance. Resonance occurs when a system is forced to vibrate by an external periodic force whose frequency matches the system’s natural frequency. At resonance, the amplitude of vibration becomes maximum, allowing efficient energy transfer. Examples include resonance in tuning forks, resonance tubes, sonometers, and forced mechanical oscillations.

Understanding standing waves and resonance helps aspirants grasp how sound amplification occurs, why certain frequencies are emphasized in musical instruments, and how energy exchange in oscillatory systems works. These standing waves and resonance concepts also form a bridge between wave motion and oscillations, making them crucial for higher-level physics problem solving.

MCQs on Standing Waves and Resonance

1. For production of beats the two sources must have

(a) Different frequencies and same amplitude
(b) Different frequencies
(c) Different frequencies, same amplitude and same phase
(d) Different frequencies and same phase

 Answer: (b)

2. The distance between the consecutive nodes is

(a) λ/2
(b) 10/n
(c) λ/10
(d) n/10

 Answer: (b)

3. A standing wave having 3 nodes and 2 antinodes is formed between two atoms separated by 1.21 Å. The wavelength is

(a) 1.21 Å
(b) 1.42 Å
(c) 6.05 Å
(d) 3.63 Å

 Answer: (a)

4. If the temperature of the medium changes, which one will change?

(a) Amplitude
(b) Frequency
(c) Wavelength
(d) Time period

 Answer: (c)

5. The correct increasing order of speed of sound in given media is

(a) 1 < 4 < 2 < 3
(b) 4 < 1 < 2 < 3
(c) 1 < 4 < 3 < 2
(d) 4 < 1 < 3 < 2

 Answer: (a)

6. Pitch is a characteristic of sound that depends upon

(a) Intensity
(b) Frequency
(c) Quality
(d) None of these

 Answer: (b)

7. A jet plane flies with velocity 2 Mach. If velocity of sound is 332 m/s, the plane’s speed is

(a) 166 m/s
(b) 66.4 km/s
(c) 332 m/s
(d) 664 m/s

 Answer: (d)

8. Which one is not produced by sound waves in air?

(a) Polarization
(b) Diffraction
(c) Reflection
(d) Refraction

 Answer: (a)

9. Sound waves are similar to waves

(a) Of laser light in air
(b) In stretched wire
(c) In a pipe with moving piston
(d) From mobile phone towers

 Answer: (c)

10. Loudness of sound is related to

(a) Frequency
(b) Amplitude
(c) Speed
(d) Pitch

 Answer: (b)

11. Which statement is NOT correct?

(a) Pitch differentiates male and female voice
(b) Loudness depends on frequency
(c) Musical sounds have harmonics
(d) Timbre depends on waveform

 Answer: (b)

12. The speed of sound in a medium depends on

(a) Elasticity only
(b) Inertia only
(c) Neither elasticity nor inertia
(d) Both elasticity and inertia

 Answer: (d)

13. When sound propagates, what is transmitted?

(a) Matter only
(b) Energy only
(c) Energy and matter
(d) Energy, momentum and matter

 Answer: (b)

14. Audible frequency range of human ear is

(a) 20–200 Hz
(b) 2–20 Hz
(c) 200–2000 Hz
(d) 20–20000 Hz

Answer: (d)

15. A yellow star accelerating towards Earth appears

(a) Suddenly red
(b) Gradually red
(c) Suddenly blue
(d) Gradually blue

Answer: (d)

16. When a train turns north to north-east

(a) Outer rail has larger radius
(b) Inner rail has larger radius
(c) Both same
(d) Inner rail infinite

 Answer: (a)

17. When a sound source moves towards observer

(a) Wavelength decreases, frequency increases
(b) Wavelength same, frequency increases
(c) Both increase
(d) Wavelength decreases, frequency same

 Answer: (a)

18. Apparent change in frequency due to relative motion is

(a) Doppler effect
(b) Beats
(c) Stationary waves
(d) Diffraction

Answer: (a)

19. Doppler effect is not applicable when source velocity is

(a) Less than sound velocity
(b) Greater than sound velocity
(c) Zero
(d) None

 Answer: (b)

20. Doppler phenomenon is related to

(a) Pitch (frequency)
(b) Loudness
(c) Quality
(d) Reflection

Answer: (a)

21. Source and detector moving with same speed in same line

(a) Detector hears same frequency
(b) Same only if source ahead
(c) Same only if detector ahead
(d) No sound heard

 Answer: (a)

22. Radar waves reflected from approaching aeroplane have wavelength

(a) λ
(b) More than λ
(c) Less than λ
(d) Depends on speed

Answer: (c)

23. Doppler effect in sound occurs when

(a) Both stationary
(b) Same velocity
(c) Relative motion exists
(d) None

 Answer: (c)

24. Doppler shift does NOT depend on

(a) Source frequency
(b) Distance between source and observer
(c) Velocity of source
(d) Velocity of observer

 Answer: (b)

25. Pulse reflected from fixed end returns with

(a) 180° phase change and velocity reversal
(b) Same phase, no reversal
(c) 180° phase change only
(d) Same phase with reversal

 Answer: (a)

26. Effect of increase in humidity on sound

(a) Speed increases
(b) Speed decreases
(c) Speed unchanged
(d) Speed becomes zero

 Answer: (a)

27. Resonance becomes sharp when

(a) Quality factor small
(b) Damping force small
(c) Restoring force small
(d) Driving force small

 Answer: (b)

28. If length and diameter of wire decrease, frequency

(a) Decreases
(b) Becomes zero
(c) Increases
(d) Remains same

 Answer: (c)

29. Resonance tube filled with denser liquid has frequency

(a) Unchanged
(b) May change
(c) Decreases
(d) Increases

 Answer: (a)

30. When sound travels from air to water, which remains constant?

(a) Time period
(b) Frequency
(c) Velocity
(d) Wavelength

 Answer: (b)

Conclusion: Importance of Standing Waves and Resonance

In conclusion, standing waves and resonance are core concepts that explain the behavior of waves in bounded systems and the conditions under which oscillations become most pronounced. Standing waves demonstrate how interference leads to stable wave patterns with fixed nodes and antinodes, while resonance explains why systems vibrate strongly at particular frequencies.

From an exam perspective, these standing waves and resonance topics are highly scoring if approached conceptually.Standing waves and resonance questions in NEET, JEE, and CUET frequently involve identifying node–antinode arrangements, calculating wavelengths, understanding resonance conditions, and analyzing how physical parameters like length, tension, density, and damping affect natural frequency. Numerical problems often combine standing wave formulas with resonance conditions, testing both understanding and calculation skills.

Beyond examinations, these standing waves and resonance principles have wide applications in acoustics, musical instrument design, engineering, and communication systems. In Standing waves and resonance, resonance plays a critical role in sound production, noise control, and even in avoiding structural failures due to unwanted oscillations. Standing waves also help explain atomic-scale phenomena and electromagnetic wave behavior.

Therefore, mastering standing waves and resonance not only helps students perform well in competitive exams but also builds a strong foundation for advanced studies in physics and engineering. A clear understanding of these standing waves and resonance concepts enhances analytical thinking and provides insight into how wave phenomena govern both natural and technological systems.