# RRB JE Exam: Physics (Sound) Quiz | 25th February

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Q1. Mechanical waves
यांत्रिक तरंगें-
(a) are longitudinal only/ केवल अनुदैर्ध्य हैं
(b) transverse only/ केवल अनुप्रस्थ
(c) can be both longitudinal and transverse/ अनुदैर्ध्य और अनुप्रस्थ दोनों हो सकते हैं
(d) none of these/इनमें से कोई नहीं

Ans(c)
Sol.A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium. Mechanical waves can be both longitudinal and transverse.

Q2. Transverse waves can propagate

अनुप्रस्थ तरंगे किस में फैल सकती हैं?
(a) both in a gas and in a metal/ गैस और धातु दोनों में
(b) in a gas but not in a metal/ गैस में लेकिन धातु में नहीं
(c) not in a gas but in a metal/ गैस में नहीं परन्तु एक धातु में
(d) neither in a gas nor in a metal/ न तो गैस में और न ही धातु में

Ans(c)
Sol. The particles in transverse waves move perpendicularly to the direction of propagation so it cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

Q3. Waves which do not require any material medium for its propagation is–

तरंगे जिनके प्रसार के लिए किसी भी भौतिक माध्यम की आवश्यकता नहीं होती है-
(a) Matter waves/ द्रव्य तरंगें
(b) Mechanical waves/ यांत्रिक तरंगें
(c) Elastic waves/ लोचदार लहरें
(d) Electromagnetic waves/ विद्युतचुम्बकीय तरंगें

Ans(d)
Sol. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.

Q4. Sound travel fastest in

ध्वनि सबसे तेज किस में यात्रा करती है ?
(a) steel/स्टील
(b) air/हवा
(c) water/पानी
(d) vacuum/ वेक्यूम

Ans(a)
Sol. The speed of sound depends on the medium in which it is transported. Sound travels fastest through solids, slower through liquids and slowest through gases.

Q5. The period of pendulum depends upon

पेंडुलम की अवधि किस पर निर्भर करती है?
(a) mass /द्रव्यमान
(b) length/लम्बाई
(c) amplitude/ आयाम
(d) energy/ ऊर्जा

Ans(b)
Sol. The period of swing of a simple gravity pendulum depends on its length.

Q6. If a pendulum is allowed to oscillate into jar containing water, its time period will

यदि एक पेंडुलम को पानी से भरे जार में डाला जाता है, तो इसकी समय अवधि ______ होगी?
(a) increase/बढ़ जाएगी
(b) decrease/घट जाएगी
(c) remain same /समान रहेगी
(d) none of these/इनमें से कोई नहीं

Ans(a)
Sol. If a pendulum is allowed to oscillate into jar containing water, its time period will increase.

Q7. If the mass of the pendulum is doubled, the time period

यदि पेंडुलम का द्रव्यमान दोगुना हो जाता है, तो समय अवधि
(a) becomes double / दोगुनी हो जाती है
(b) becomes half /आधी हो जाती है
(c) becomes four times /चार गुणा हो जाती है
(d) remains same/समान रहेगी

Ans(d)
Sol. T is the time period of the pendulum, L is the pendulum length and g is the acceleration due to gravity. Hence, time period of a pendulum is independent of the mass of its bob. Thus, if we increase the mass of the bob of a pendulum by a factor of 3, its time period will remain unchanged.

Q8. The phenomenon in which the amplitude of oscillation of pendulum decreases gradually is called

वह घटना जिसमें पेंडुलम के परिसंचरण का आयाम धीरे-धीरे कम हो जाता है क्या कहलाता है?
(a) decay period of oscillation/ परिसंचरण की क्षय अवधि
(b) damping/ डेम्पिंग
(c) building up oscillation/ परिसंचरण का निर्माण
(d) maintained oscillation/ परिसंचरण बनाए रखा

Ans(b)
Sol. Damping is any effect that tends to reduce the amplitude of vibrations. In mechanics, the internal friction may be one of the causes of such damping effect.

Q9. The product of the time period of a wave and its frequency is

किसी तरंग की समयावधि और उसकी आवृत्ति का गुणनफल क्या होता है?
(a) infinite/ अनंत
(b) zero/शून्य
(c) unity/यूनिटी
(d) None /कोई नहीं

Ans(c)
Sol. Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency.so The product of the time period of a wave and its frequency is unity.

Q10. Out of the following, which frequency is not clearly audible to the human ear?

निम्नलिखित में से, कौन सी आवृत्ति स्पष्ट रूप से मानव कान के लिए श्रव्य नहीं है?
(a) 30 Hz
(b) 30,000 Hz
(c) 300 Hz
(d) 3000 Hz

Ans(b)
Sol. Sound waves with frequency ranging from 20 Hz to 20 KHz is known are audible sound. More then 20KHz is not audible sound.

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