physics- Waves

Science

यदि सिग्नल की आवृत्ति 50 Hz है तो उसके आवर्तकाल का क्या मान होगा?कनिष्ठ अनुदेषक (इलेक्ट्रोनिक्स मैकेनिक) 23-12-19

  • 0.02 sec
  • 0.2 sec
  • 50 sec
  • 20 sec

दूरदर्शन प्रसारण में, चित्र संदेशों का संचरण होता है ? RPSC Live Stock Asst. 2016

  • आयाम माडुलन द्वारा
  • आवृति माडुलन द्वारा
  • कला माडुलन द्वारा
  • कोण माडुलन द्वारा

क्रिस्टल की संरचना जानने के लिए निम्न में से किसको प्रयोग में लाया जाता है ? BSTC

  • गामा- किरणें
  • एक्स-किरणें
  • UV – किरणें
  • दृश्य प्रकाश

हम लघु तरंग के प्रसारणों को दीर्घ तरंग के प्रसारणों की अपेक्षा अधिक अच्छी तरह क्यों सुन सकते है?

  • दीर्घ तरंगों कीअपेक्षा लघु तरंगों में अधिक ऊर्जा
  • लघु तरंगो पर वायु मण्डल विक्षोभ का प्रभाव नहीं पड़ता
  • लघु तरंग के प्रसारण निकटस्थ रेडियो केन्द्रों द्वारा किये जाते है
  • परम्परागत से लघु तरंग लम्बी दूरियों के लिये है और दीर्घ तरंगे छोटी दूरियों के लिये आरक्षित हैं

उच्चतम वेधन क्षमता की तरंग है? Raj. IInd Gr. Teacher Science 2010

  • अवरक्त तरंग
  • पराबैंगनी तरंग
  • एक्स किरण
  • गामा किरण

बहुत उच्च आवृत्ति की तरंग दैर्ध्य क्या होती है- [ Female MPHW 2016]

  • सबसे छोटी
  • छोटी
  • सबसे लंबी
  • लंबी

बैंगनी रंग के प्रकाश की तरंगदैर्ध्य लगभग होता है । [UP Police 28-01-2019]

  • 10-11 pm
  • 1-10 mm
  • 390-455 nm
  • 230-310 pm

निम्नलिखित में से किस माध्यम में ध्वनि की गति उच्चतम होती है? by Raj. B.Ed 2008, RPSI- 1996, 2002

  • वायु
  • इस्पात
  • पानी
  • निर्वात

900 Hz आवृत्ति कहलाती है- कनिष्ठ अनुदेशक (वायरमैन) 24-12-2019

  • श्रव्य आवृत्ति
  • रेडियो आवृत्ति
  • उच्च आवृति
  • परा उच्च आवृत्ति

श्रव्य आवृत्तियों का आवृत्ति परास क्या है? कनिष्ठ अनुदेशक (इलेक्ट्रोनिक्स मैकेनिक)

  • 0Hz 100 kHz
  • 500Hz – 100 kHz.
  • 350 Hz – 350 kHz
  • 20 Hz – 20 kHz

गूँजहीन हॉल का अनुरणन काल होता है? Raj. IInd Gr. Teacher 2017

  • शून्य सेकण्ड
  • 0.8 सेकण्ड
  • 1.8 सेकण्ड
  • 8 सेकण्ड

वायु में ध्वनि की चाल है? JVVNL 2013

  • 664 mtr/Sec.
  • 332 mtr/Sec.
  • 166 mtr/Sec.
  • 100 mtr/Sec.

मनुष्यों के लिये शोर की सहन सीमा करीब-करीब होती है? Raj. Illrd Gr. Teacher 2010 , R.A.S./R.T.S. (Pre) 1993

  • 45 डेसीबल्स
  • 85 डेसीबल्स
  • 125 डेसीबल्स
  • 155 डेसीबल्स

1. What is the SI unit of frequency?

  • Decibel
  • Hertz
  • Second-1
  • Metre

Explanation:

  • Hertz (Hz) is the SI unit of frequency, defined as one cycle per second.
  • Decibel is the unit for sound intensity level.
  • Second-1 (s-1) represents the dimension of frequency but is not its named SI unit.
  • Metre is the SI unit of length.

2. The speed of sound is maximum in which medium?

  • Vacuum
  • Air
  • Water
  • Steel

Explanation:

  • Steel is a solid, and sound travels fastest in solids due to the close packing of molecules.
  • Sound cannot travel in a vacuum as it requires a medium.
  • Speed in air is about 343 m/s and in water (a liquid) it is about 1500 m/s, both slower than in solids like steel (~6000 m/s).

3. Which phenomenon explains why sound is heard at longer distances at night?

  • Echo
  • Refraction
  • Reflection
  • Reverberation

Explanation:

  • Refraction of sound waves occurs due to the temperature gradient in the atmosphere. At night, the air near the ground is cooler, causing sound waves to bend downward.
  • Echo and Reflection are the bouncing back of sound waves.
  • Reverberation is the persistence of sound due to repeated reflections.

4. The persistence of audible sound due to repeated reflections is called?

  • Echo
  • Resonance
  • Reverberation
  • Refraction

Explanation:

  • Reverberation is the phenomenon where sound continues to be heard as a result of multiple reflections even after the original sound has ceased.
  • Echo is a distinct, single reflection of sound heard after a delay.
  • Resonance is the increase in amplitude when a driving frequency matches natural frequency.

5. Infrasonic waves are sound waves with a frequency:

  • Above 20,000 Hz
  • Between 20 Hz and 20,000 Hz
  • Below 20 Hz
  • Equal to 440 Hz

Explanation:

  • Below 20 Hz. The human audible range is 20 Hz to 20,000 Hz. Sound waves with frequency below 20 Hz are called infrasonic.
  • Above 20,000 Hz are ultrasonic waves.
  • 440 Hz is the standard frequency for the musical note A4.

6. The pitch of a sound is determined by its:

  • Amplitude
  • Frequency
  • Speed
  • Timbre

Explanation:

  • Frequency is the physical property that determines the pitch of a sound. A higher frequency corresponds to a higher pitch.
  • Amplitude determines the loudness.
  • Timbre or quality helps distinguish between different sounds of the same pitch and loudness.

7. Which part of the human ear amplifies sound vibrations?

  • Cochlea
  • Eardrum
  • Ossicles
  • Auditory Nerve

Explanation:

  • The Ossicles (a set of three tiny bones: malleus, incus, and stapes) in the middle ear act as a lever system to amplify the sound vibrations received from the eardrum.
  • The cochlea converts vibrations into electrical signals.
  • The eardrum vibrates in response to sound waves.

8. The technique used by bats to navigate and hunt is:

  • Echolocation
  • Sonar
  • Radar
  • Refraction

Explanation:

  • Echolocation is the biological sonar used by bats. They emit ultrasonic squeaks and interpret the echo to locate prey and navigate.
  • Sonar (Sound Navigation and Ranging) is the human-made technology used underwater, based on the same principle.
  • Radar uses radio waves, not sound.

9. When a sound wave goes from air to water, which property remains unchanged?

  • Wavelength
  • Velocity
  • Frequency
  • Amplitude

Explanation:

  • Frequency is the fundamental property of a wave that depends on the source. It does not change when the wave moves from one medium to another.
  • Velocity and wavelength change as the wave crosses the boundary between media.
  • Amplitude may change due to energy transfer.

10. The loudness of sound is measured in:

  • Hertz
  • Metres
  • Decibels
  • Metres per second

Explanation:

  • Decibels (dB) are the units used to measure the intensity level of sound, which is perceived as loudness.
  • Hertz measures frequency.
  • Metres measure wavelength.

11. A man standing between two parallel cliffs hears the first echo after 2 seconds and the second echo after 3 seconds. What is the distance between the cliffs? (Speed of sound = 340 m/s)

  • 850 m
  • 340 m
  • 170 m
  • 680 m

Explanation:

  • 850 m. Distance to first cliff, d1 = (v*t1)/2 = (340*2)/2 = 340m. Distance to second cliff, d2 = (v*t2)/2 = (340*3)/2 = 510m. Total distance between cliffs = d1 + d2 = 340 + 510 = 850m.

12. The phenomenon of sound bending around obstacles is called:

  • Reflection
  • Refraction
  • Diffraction
  • Interference

Explanation:

  • Diffraction is the bending of waves around obstacles and the spreading out of waves past small openings.
  • Reflection is the bouncing back of waves.
  • Refraction is the bending of waves due to a change in medium.

13. Which type of waves are sound waves?

  • Transverse waves
  • Longitudinal waves
  • Electromagnetic waves
  • Polarized waves

Explanation:

  • Longitudinal waves. In a sound wave, the particles of the medium vibrate parallel to the direction of wave propagation, forming compressions and rarefactions.
  • Light is a transverse electromagnetic wave.

14. The characteristic of a sound that enables us to distinguish between a sharp and a flat note is:

  • Loudness
  • Pitch
  • Timbre
  • Echo

Explanation:

  • Pitch is the perception of the frequency of a sound. A higher frequency sound is perceived as a sharper (higher pitched) note, and a lower frequency is a flatter (lower pitched) note.
  • Loudness relates to amplitude.
  • Timbre relates to quality.

15. The minimum distance required to hear a distinct echo is approximately: (Take speed of sound = 340 m/s)

  • 34 m
  • 17 m
  • 340 m
  • 680 m

Explanation:

  • 17 m. The human ear can distinguish two sounds if they are received at least 0.1 seconds apart. Minimum distance = (speed * time)/2 = (340 m/s * 0.1 s)/2 = 17 m.

16. Which of the following has no effect on the speed of sound?

  • Pressure of the gas
  • Temperature of the medium
  • Density of the medium
  • Frequency of the sound

Explanation:

  • Frequency of the sound. The speed of sound in a medium depends on the elastic and inertial properties of that medium (e.g., temperature, density). It is independent of the frequency (pitch) or amplitude (loudness) of the sound wave.

17. The frequency of a sound wave is 440 Hz. What is its time period?

  • 440 s
  • 0.44 s
  • 1/440 s
  • 220 s

Explanation:

  • 1/440 s. The time period (T) is the reciprocal of frequency (f). T = 1/f = 1/440 seconds.

18. The quality or timbre of a sound depends on its:

  • Frequency
  • Amplitude
  • Waveform
  • Speed

Explanation:

  • Waveform. Timbre is the characteristic that allows us to distinguish between musical notes of the same pitch and loudness played on different instruments. It is determined by the shape of the wave or the number of overtones present.

19. SONAR is based on the principle of:

  • Resonance
  • Echo
  • Refraction
  • Beats

Explanation:

  • Echo. SONAR (Sound Navigation and Ranging) works by sending out ultrasonic sound waves and then receiving their echoes after reflection from underwater objects to determine their distance and location.

20. The velocity of sound in air increases with:

  • Increase in humidity
  • Decrease in temperature
  • Decrease in pressure
  • Increase in wind velocity

Explanation:

  • Increase in humidity. The speed of sound increases slightly with an increase in humidity because the density of moist air is less than that of dry air. Speed increases with temperature, not decreases.

21. The phenomenon of beats is a result of:

  • Reflection
  • Refraction
  • Interference
  • Diffraction

Explanation:

  • Interference. Beats are produced due to the superposition (interference) of two sound waves of slightly different frequencies traveling in the same direction. The periodic variation in intensity results in the wavering beat sound.

22. Which of the following is NOT an application of ultrasound?

  • SONAR
  • Medical Imaging
  • Cleaning delicate objects
  • AM Radio Broadcast

Explanation:

  • AM Radio Broadcast. AM radio uses amplitude modulation of electromagnetic waves in the kHz range, not ultrasonic sound waves. All other options are common applications of ultrasound.

23. The number of vibrations completed in one second is called:

  • Wavelength
  • Time Period
  • Amplitude
  • Frequency

Explanation:

  • Frequency. It is defined as the number of complete oscillations or cycles per second. Its unit is Hertz (Hz).
  • Time period is the time taken for one complete oscillation.

24. A sound wave is an example of a:

  • Standing wave
  • Shock wave
  • Mechanical wave
  • Stationary wave

Explanation:

  • Mechanical wave. A sound wave requires a material medium (solid, liquid, or gas) to propagate. Therefore, it is classified as a mechanical wave.
  • Standing/Stationary waves are a specific pattern formed under certain conditions.

25. The speed of sound in a given medium depends on:

  • Its frequency
  • Its wavelength
  • The properties of the medium
  • Its amplitude

Explanation:

  • The properties of the medium. The speed of sound is determined by the elasticity and density of the medium through which it is traveling (v = √(E/ρ)). It is independent of the frequency, wavelength, and amplitude of the sound wave itself.
physics- Waves