# Physics [Gravitation] Questions for Railway ALP Stage-II Exam : 23rd November 2018

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Q1. The characteristic of sound which distinguishes a female voice from a male voice is called
ध्वनि की वह विशेषता जो नर ध्वनि और मादा ध्वनि को अलग करती है उसे क्या कहा जाता है?
(a) pitch/ पिच
(b) phase/फेज
(c) quality/ गुणवत्ता
(d) loudness/ प्रबलता
S1. Ans.(a)
Sol. The pitch is the reason behind the difference in voice quality of different individuals. The pitch of a sound depends on the frequency while loudness of a sound depends on the amplitude of sound waves.

Q2. Stationary wave is formed by
स्थिर तरंग का गठन होता है-
(a) a transverse wave superposing a longitudinal wave/ एक अनुदैर्ध्य तरंग के ऊपर एक अनुप्रस्थ तरंग
(b) two waves of the same speed superposing/ एक दुसरे के ऊपर दो समान गति की तरंगें
(c) two waves of same frequency travelling in the same direction /एक ही दिशा में यात्रा करने वाली समान आवृत्ति की दो तरंगें
(d) two waves of same frequency travelling in the opposite direction / विपरीत दिशा में यात्रा करने वाली समान आवृत्ति की दो तरंगें

S2. Ans.(d)
Sol. Stationary or standing waves are formed in a medium when two waves having equal amplitude and frequency moving in opposite directions along the same line, interfere in a confined space. Generally, such waves are formed by the superposition of a forward wave and the reflected wave.

Q3. Velocity of sound in air does not depend on
हवा में ध्वनि का वेग किस पर निर्भर नहीं है
(a) humidity of air/ हवा की आर्द्रता
(b) temperature of air/ हवा का तापमान
(c) pressure of air/ हवा का दबाव
(d) none of these/ इनमे से कोई नहीं

S3. Ans.(c)
Sol. Assuming air to be an ideal gas the velocity of sound in air can be represented as v=√(γRT/M) That means That the speed of sound in air is fundamentally a function of temperature T and it does not depend on the air pressure as the air pressure.

Q4. The bats can fly in the dark, because
चमगादड़ अंधेरे में उड़ सकते हैं, क्योंकि
(a) they can see the objects in darkness / वे अंधेरे में वस्तुओं को देख सकते हैं
(b) they have weak legs and are likely to be attacked by predators/ उनके पैर कमजोर हैं और शिकारियों द्वारा हमला किया जा सकता है
(c) they generate flashes of light / वे प्रकाश की चमक उत्पन्न करते हैं
(d) they generate ultrasonic sound waves/ वे अल्ट्रासोनिक ध्वनि तरंगें उत्पन्न करते हैं

S4. Ans.(d)
Sol. The bats can fly in the dark, because they generate the ultrasonic sound waves having the frequency greater than 20000 Hz. Human ear cannot detect these waves. In the case of total darkness, bats use echolocation to navigate and forage. The use of echolocation allows them to occupy a niche where there are often many insects coming out at night since there are fewer predators.

Q5. The propagation of sound waves in a gas involves
गैस में ध्वनि तरंगों के प्रसार में शामिल है
(a) adiabatic compression and rarefaction/ एडिएबैटिक संपीड़न और विरलीकरण
(b) isothermal compression and rarefaction/ समतापीय संपीड़न और विरलीकरण
(c) isochoric compression and rarefaction/आइसोकोरिक संपीड़न और विरलीकरण
(d) isobaric compression and rarefaction/ समदाब संपीड़न और विरलीकरण

S5. Ans.(a)
Sol. The propagation of sound waves in a gas involves the adiabatic compression and rarefaction. The bulk modulus of a gas depends on the pressure of the gas The greater the pressure applied to a gas to compress it, more, it resists further compression and hence greater the bulk modulus.
The density of a gas also depends on the pressure. Which in turn depends on the pressure. Which in turn depends on the temperature. The longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure causing local regions of compression and rarefaction.

Q6.When there is depletion of ozone in the stratosphere, the wavelength of radiation striking the earth’s surface will be
जब समताप मंडल में ओजोन की कमी हो जाती है, तो पृथ्वी की सतह पर टकराने वाले विकिरण की तरंगदैर्ध्य कितनी होती है?
(a) 10–10 m
(b) 10–7 m
(c) 10–2 m
(d) 100 m

Ans.(b)
Sol. Ultraviolet radiations are mainly divided into three groups:- UV-A radiations : the long wave UV-A radiations having the wavelength of 320-400 nm. They strike the surface of the earth as the part of the rays of the sun.
UV-B radiations: the medium wave UV-B radiation has the wavelength of 280-320 nm. It is mostly absorbed by the ozone layer, but some do reach the earth’s surface.
UV-C radiations – it has a wavelength of 100-280 nm. It is completely absorbed by ozone layer and atmosphere.
Therefore, on depletion of ozone in the stratosphere, the wavelength of radiation striking the surface of the earth will be 100 nm.
1 nm = 1.0 ×  m
100 nm = 100 × 10-9 =10-7 m

Q7. What is the full form of AM regarding radio broadcasting ?
रेडियो प्रसारण के संबंध में AM का पूर्ण रूप क्या है?
(a) Amplitude movement
(b) Anywhere movement
(c) Amplitude matching
(d) Amplitude modulation
S7. Ans.(d)
Sol. In the radio broadcasting, AM stands fore amplitude modulation which was the first method of impressing sound on a radio signal and is still widely used today. The amplitude variations at a particular frequency in the radiowaves are detected by the AM receiver and then the changes are amplified in the signal voltage to drive a loudspeaker or earphones.

Q8. The audio signals of TV are
टीवी के ऑडियो सिग्नल हैं
(a) amplitude modulated/ एम्पलीत्युड मॉड्यूटेड
(b) frequency modulated / आवृत्ति मॉड्यूटेड
(c) unmodulated/ अनमॉड्यूटेड
(d) velocity modulated/ वेग मॉड्यूटेड
S8. Ans.(b)
Sol.  In the telecommunications and signal processing the audio signals of TV are frequency modulated which conveys information over a carrier wave by varying its instantaneous frequency. In analogue television, the analogues transmission is involved which is the broadcasting of encoded analogue audio and analogue video signal.
The message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and or frequency of the signal.
Here, the sound portion of a broadcast is invariably modulated separately from the video.

Q9. Why are we able to hear short wave broadcast better than long wave broadcasts ?
हम उच्च तरंग प्रसारण से बेहतर लघु तरंग प्रसारण को क्यों सुन सकते हैं
(a) Short waves are more energetic than long waves/ लघु तरंग उच्च तरंग की तुलना में अधिक ऊर्जावान हैं
(b) Short waves are unaffected by atmospheric disturbances/ लघु तरंग वायुमंडलीय बाधा से अप्रभावित हैं
(c) Short waves broadcasts are made by nearby radio stations/ लघु तरंगों के प्रसारण पास के रेडियो स्टेशनों द्वारा किए जाते हैं
(d) By convention, short waves are meant for long distance, whereas long waves are reserved for short distances / अभिसमय से, लघु तरंगें लंबी दूरी के लिए होती हैं, जबकि उच्च तरंगें कम दूरी के लिए आरक्षित होती हैं
S9. Ans.(a)
Sol. Short wave bands are frequency allocations for use within the shortwave radio spectrum. Propagation behaviour on the shortwave bands depends on the time of day, the season and the level of solar activity. The short waves being more energetic than the longer waves can be easily heard better then those of longer waves broadcasts.

Q10. When a vehicle passes, TV reception gets distorted. This is because
जब कोई वाहन गुजरता है, टीवी रिसेप्शन विकृत हो जाता है। क्योंकि-
(a) metal reflects radiowaves/ धातु रेडियो तरंगें प्रतिबिंबित करता है
(b) spark plug creates electromagnetic disturbances/ स्पार्क प्लग विद्युत चुम्बकीय बाधा उत्पन्न करता है
(c) vehicle pollution affects the performance of the TV components / वाहन प्रदूषण टीवी घटकों के प्रदर्शन को प्रभावित करता है
(d) modern vehicles use electroignition system/ आधुनिक वाहन इलेक्ट्रोइग्निशन सिस्टम का उपयोग करते हैं
S10. Ans.(b)
Sol. When a vehicle passes, TV reception gets distorted due to the phenomenon of interference caused by the electromagnetic waves produced by the passing vehicle. Interference is the event where two waves of equal frequency superimpose to form a resultant wave of greater or lower amplitude. The effects of interference can be experienced with all types of waves, for example, light, radio, acoustic and surface water wave.

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