# Physics Questions [Wave Motion] for Railway ALP Stage-II Exam : 15th November 2018

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Q1. Long radio waves are reflected by which of the following layer of earth’s surface—
निम्न परतों में से लंबी रेडियो तरंगें पृथ्वी की किस सतह पर दिखाई देती हैं?
(a) Troposphere / ट्रोपोस्फीयर
(b) Ionosphere / आयनोस्फीयर
(c) Tropopause / ट्रोपोपोज
(d) Stratosphere / स्ट्रेटोस्फीयर
Ans.(b)
Sol. The ionosphere is a region of earth’s upper atmosphere from about 65 km. to 400 km altitude. It is ionized by solar radiation. It has practical importance because among other functions, it influences radio propagation to distant places on earth.

Q2. Wireless communication is reflected back to the earth’s surface by the—
वायरलेस संचार पृथ्वी की सतह पर वापस किसके द्वारा परिलक्षित होता है?
(a) Troposphere / ट्रोपोस्फीयर
(b) Stratosphere / स्ट्रेटोस्फीयर
(c) Ionosphere / आयनोस्फीयर
(d) Exosphere / एक्सोस्फीयर

Ans.(c)
Sol. The ionosphere is a region of earth’s upper atmosphere from about 65 km. to 400 km altitude. It is ionized by solar radiation. It has practical importance because among other functions, it influences radio propagation to distant places on earth.

Q3. With the rise of temperature, the speed of sound in a gas?
तापमान के बढ़ने के साथ, गैस में ध्वनि की गति में क्या परिवर्तन आता है ?
(a)increase / वृद्धि होती है
(b)decreases / घटता है
(c)remains the same / वही रहता है
(d)None of these / इनमें से कोई नहीं

Ans.(a)
Sol. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly. The speed of sound in room temperature air is 346 meters per second.

Q4. Which waves cannot be transmitted through vaccum ?
वैक्यूम के माध्यम से कौन सी तरंगों को प्रेषित नहीं किया जा सकता है?
(a) Light / प्रकाश
(b) Heat / ऊष्मा
(c) Sound / ध्वनि
(d) Electromagnetic / विद्युत चुम्बकीय

Ans.(c)
Sol. Sound waves cannot be transmitted through vacuum. It is transmitted by the movement of particles along with the direction of the motion of the sound wave. More generally, sound is a mechanical disturbance which is dependent upon a medium to travel. It can be transmitted through solids, liquids, and gases.

Q5. Cosmic rays —
ब्रह्मांडीय किरणें
(a) Are charged particles / आवेशित कण
(b) Are uncharged particles / अनावेशित कण
(c) Can be charged as well as uncharged/ आवेशित भी किया जा सकता है साथ ही अनावेशित भी किया जा सकता है.
(d) None of the above / उपर्युक्त में से कोई नहीं

Ans.(a)
Sol. Cosmic rays are not the part of electromagnetic spectrum. They are immensely high-energy radiation waves, mainly originating outside the solar system.

Q6. Which one of the following statements is not true about cosmic rays ?
ब्रह्मांडीय किरणों के बारे में निम्नलिखित में से कौन सा कथन सत्य नहीं है?
(a) They are electromagnetic waves  / वे विद्युत चुम्बकीय तरंगें हैं
(b) They have very short wavelength / उनके पास बहुत कम तरंगदैर्ध्य
(c) They are made of highly energetic charged particles. / वे अत्यधिक ऊर्जावान चार्ज कणों से बने होते हैं।
(d) They originate from the sum / वे योग से उत्पन्न होते है

Ans.(a)
Sol. Cosmic rays are not the part of electromagnetic spectrum. They are immensely high-energy radiation waves, mainly originating outside the solar system.

Q7. What is the distance between two successive crests or successive troughs called ?
दो लगातार शीर्ष या लगातार गर्त के बीच की दूरी क्या है?
(a) Amplitude / आयाम
(b) Wavelength / तरंग दैर्ध्य
(c) Frequency / आवृत्ति
(d) None of these / इनमें से कोई नहीं
Ans.(b)
Sol. Wavelength means the distance measured in the direction of a wave from any given point to the next point in the same phase, as from crest to crest. The distance between two successive crests or two successive troughs is the wavelength for a transverse wave.
Q8. Which one of the following is used for determining the structure of crystal :
क्रिस्टल की संरचना का निर्धारण करने के लिए निम्नलिखित में से किसका उपयोग किया जाता है:
(a) Gamma rays / गामा किरणें
(b) X-rays / एक्स-रे
(c) UV rays / यूवी किरणें
(d) visible light / दृश्य प्रकाश
Ans.(b)
Sol. Crystallography is the science that examines crystals which can be found everywhere in nature, from salt to snowflakes to gemstones. Crystallographers use the properties of the inner structure of crystals to determine the arrangement of atoms and generate knowledge which is used by chemist, physicists and other. Crystallographers use X-ray, neutron, and electron diffraction techniques to identify the characteristics of solid materials.

Q9. A radar which detects the presence of an enemy aircraft uses :
एक रडार जो दुश्मन के विमान की उपस्थिति का पता लगाता है:
(a) Light waves / लाइट तरंगें
(b) Radio waves / रेडियो तरंगें
(c) Sound waves / ध्वनि तरंगें
(d) Ultrasound waves / अल्ट्रासाउंड तरंगें
Ans.(b)
Sol. Radar is an object-detection system which uses radio waves to determine the range, angle or velocity of objects. It is used to detect the location of aircraft, ships, spacecraft, motor vehicle etc.

Q10. 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 हमला करने वाले विकिरण की तरंगदैर्ध्य कितनी होती है?
(a) 10–10 m/मीटर
(b) 10–7 m/ मीटर
(c) 10–2 m / मीटर
(d) 100 m/ मीटर
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 × 10^(-9) m
100 nm = 100 × 10^(-9)
= 10^2×10^(-9)
= 10^(-7) m

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