Waves Basics — Set 4
Physics · तरंगों की मूल बातें · Questions 31–40 of 60
Which instrument is commonly used to study resonance in an air column and estimate the speed of sound?
Correct Answer: A. Resonance tube
Resonance tube is correct because it uses standing waves in an air column. Resonance happens at specific lengths that match wave patterns. The measured resonant lengths help calculate wavelength and speed.
The approximate audible frequency range for humans is?
Correct Answer: D. 20 Hz to 20 kHz
20 Hz to 20 kHz is correct because it is the typical human hearing range. Below this range is infrasonic and above it is ultrasonic. Hearing limits vary with age and individual differences.
For many simple waves, the energy transported by a wave is proportional to the square of its?
Correct Answer: A. Amplitude
Amplitude is correct because larger amplitude means larger oscillation and more energy. In many models, intensity is proportional to amplitude squared. This is why small amplitude changes can greatly change loudness.
When two waves of the same frequency and amplitude meet in opposite phase, the result is?
Correct Answer: C. Destructive interference
Destructive interference is correct because opposite phase makes displacements cancel. The net amplitude can become small or zero at some points. Constructive interference happens when waves are in phase.
Huygens’ principle is mainly used to explain?
Correct Answer: A. Propagation of wavefronts
Propagation of wavefronts is correct because each point on a wavefront acts like a source of secondary wavelets. The new wavefront is the envelope of these wavelets. This idea helps explain reflection and refraction of waves.
A vibration has time period 0.02 s. What is the frequency?
Correct Answer: B. 50 Hz
Option B is correct because f = 1/T = 1/0.02 = 50 Hz. Frequency is the number of cycles per second. Smaller time period means higher frequency.
SONAR systems primarily use which type of waves for detecting underwater objects?
Correct Answer: B. Ultrasonic waves
Ultrasonic waves are correct because high frequency sound reflects well from objects in water. Time of return of the echo helps estimate distance. This method is based on reflection of sound waves.
Which equation is a fundamental relation for many waves?
Correct Answer: C. v = fλ
v = fλ is correct because it links speed, frequency, and wavelength. It means each cycle advances one wavelength in space. If frequency stays fixed, changing speed changes wavelength.
For the fundamental mode on a string fixed at both ends, the length L equals?
Correct Answer: C. λ/2
L = λ/2 is correct because a half-wavelength fits between two fixed ends. The ends are nodes where displacement is zero. Higher modes fit more half-wavelengths into the same length.
For a closed organ pipe of length L, the fundamental frequency is?
Correct Answer: C. f = v/4L
f = v/4L is correct because a closed pipe supports a quarter-wavelength in the fundamental. The closed end is a displacement node and the open end is an antinode. The fundamental wavelength is λ = 4L.