Physics: Light Questions for Railway & SSC CGL Exam 2018: 10th July

Railway Board offers opulent and revered job posts to its aspirants. And it is not every year that we get the notification from Railway offering a good number of vacant seats to the multitude aspirants. But the current year 2018 brought a pleasant surprise with almost 90,000 seats to be filled by the valid candidates. Opportunity is here but you have to welcome it with a provident strategy. The exam will be conducted in the month of May 2018. 

रेलवे बोर्ड अपने उम्मीदवारों के लिए भव्य और प्रतिष्ठित कार्य पदों की पेशकश करता है. और हर साल ऐसा नहीं होता है कि हमें रेलवे की ओर से अधिसूचना मिलती है. लेकिन वर्तमान वर्ष 2018 आपके लिए बहुत सुखद वर्ष है क्योंकि इसमें लगभग 90,000 सीटों को वैध उम्मीदवारों द्वारा भरा जाएगा. आपके पास बहुत अच्छा अवसर है और आपको इसे एक बेहतर रणनीति से प्राप्त करना होगा. परीक्षा मई 2018 के महीने में आयोजित की जायेगी.

Q1. Waves used for telecommunication are- 
दूरसंचार के लिए किस प्रकार की तरंगों का उपयोग किया जाता हैं - 
(a) Visible light /दृश्य प्रकाश
(b) Infrared/इन्फ्रारेड
(c) Ultraviolet/पराबैंगनी
(d) Microwave/माइक्रो तंरग
Show Answer
Sol. The microwaves are high-frequency signals in the 300 MHz to 300 Ghz range. The signals can carry thousands of channels at the same time, making it a very versatile communication system. Microwave is often used for point-to-point telecommunications. Today microwave is employed by telecommunication industry in the form of both terrestrial relays and satellite communication.

Q2. The technique used to transmit audio signals in television broadcast is- 
टेलीविज़न प्रसारण में ऑडियो सिग्नल संचारित करने के लिए किस तकनीक का इस्तेमाल होता है - 
(a) Amplitude modulation/आयाम मॉड्‍यूलन
(b) Pulse code modulation/पल्स कोड मॉडुलेशन
(c) Frequency modulation/आवृति मॉडुलेशन
(d) Time dimension multiplication/समय आयाम बहुलीकरण
Show Answer
Sol. Television broadcasts emit two types of signals, audio and visual. These two signals require modulation to transmit both signals at the same time. Analog television requires transmission that uses specific modulation methods employing AM and FM signals in its transmission. Frequency modulation or FM is used for the audio part of the transmission. Amplitude modulation or AM is used in the video transmission. 

Q3. Bats can fly during dark nights and also prey. This is because- 
चमगादड़ रात के अँधेरे के दौरान उड़ान भर सकते हैं और शिकार भी कर सकते हैं. यह है क्योंकि-
(a) The pupil of their eyes is large / उनकी आंखों की पुतली बड़ी होती है.
(b) Their night vision is very good / उनकी रात्रि दृष्टि बहुत अच्छी है
(c) Every bird can do this / प्रत्येक पक्षी यह कर सकता है.
(d) They produce ultrasonic waves and are guided by them / वे अल्ट्रासोनिक तरंगें पैदा करते हैं और इनके द्वारा निर्देशित होते हैं
Show Answer
Sol. Bats are a fascinating group animals. They are one of the few mammals that can use ultrasonic sound to navigate. As they fly, make an ultrasonic (shouting) sound. The returning echoes give the bats information about anything that is ahead of them, including the speed and size of an insect and which way it is going. This system of finding prey is called echolocation-locating things by their echoes.

Q4. Which one of the following is the effect of the flight of supersonic jet?  
निम्नलिखित में से क्या सुपरसोनिक जेट की उड़ान का प्रभाव है?  
(a) Air pollution/वायु प्रदुषण
(b) Eye disease/नेत्र रोग
(c) Depletion in ozone layer/ओजोन परत में कमी
(d) None of these/इनमे से कोई नहीं
Show Answer
Sol. A jet engine is a machine for turning fuel into thrust. The thrust is produced by action and reaction also known as Newton’s third law of motion. Those jet planes which are able to fly faster than the speed of sound are called supersonic jet planes. Jet engines are responsible for depletion of ozone. Flying at stratosphere height, they emits nitrogen oxide which has the potential to destroy significant quantities of ozone in the stratosphere.

Q5. Which of the following has the longest wavelength? 
निम्नलिखित में से किसकी सबसे लंबी तरंग दैर्ध्य है? 
(a) Infrared/इन्फ्रारेड
(b) X-rays/एक्स-रे
(c) Visible light/दृश्य प्रकाश
(d) Radio waves/ रेडियो तरंगें
Show Answer
Sol. The electromagnetic spectrum consists of all the different wavelength of electromagnetic radiations such as: Radiowaves > Microwave > Infrared > Visible > Ultraviolet > X-rays > Gamma rays. Thus it is clear that the radio-waves are having the maximum wavelength while the Gamma rays are having minimum wavelength.

Q6. The tolerable limit of noise for human being is around- 
मानव के लिए शोर की सहनीय सीमा लगभग _____ है
(a) 45 decibel / 45 डेसीबल
(b) 85 decibel /85 डेसीबल
(c) 125 decibel / 125 डेसीबल
(d) 155 decibel/155 डेसीबल
Show Answer
Sol. The sound of 50 decibel is enough to wake up a sleeping person. To remain continuously in the sound of 80 decibel proves to be harmful. 85 decibel is the maximum limit to tolerate any noise by human being.

Q7. A radio station broadcast at 30 metre band. The frequency of the carrier wave transmitted by this station is:- 
एक रेडियो स्टेशन 30 मीटर बैंड पर प्रसारण करता है. इस स्टेशन द्वारा प्रेषित वाहक तरंग की आवृत्ति कितनी होती है:-
(a) 10 KHz  /10 किलोहर्ट्ज
(b) 100 KHz /  100 किलोहर्ट्ज
(c) 10 MHz /10 मेगाहट्र्ज
(d) 100 MHz/ 100 मेगाहट्र्ज
Show Answer
Sol. According to formula = > n = c/I
[where n=frequency,c=speed of light;I=wavelength]
=(3×10^8)/30=10×10^6=10 MHz

Q8. The concept of expanding universe is based on- 
ब्रह्मांड के विस्तार की अवधारणा किस पर आधारित है - 
(a) Doppler effect/डॉपलर प्रभाव
(b) Stark effect/बिल्कुल प्रभाव
(c) Zeeman effect/जीमन प्रभाव
(d) Raman effect/रमन प्रभाव
Show Answer
Sol. The concept of expanding universe is based on Doppler effect. It was named after Christian Doppler, who first came up with the idea in 1942. Edwin Hubble used the Doppler Effect to determine that universe is expanding. Hubble found that the light from distant galaxies was shifted towards lower frequencies, to the red end of the spectrum. This is known as a red Doppler shift or a red-shift.

Q9. A biotechnique in which ultrasonic sound is used- 
एक बायोटेक्निक जिसमें अल्ट्रासोनिक ध्वनि का उपयोग किया जाता है - 
(a) Sonography/ सोनोग्राफी
(b) E.C.G / ई.सी.जी
(c) E.E.G / ई.ई.जी.
(d) X-ray/एक्स-रे
Show Answer
Sol. Sonography or ultrasonography is an important mean of clinical diagnosis. It is a diagnostic imaging technique based on the application of ultrasound. It is widely used in the field of medical science.

Q10. CT Scan is done by using- 
CT स्कैन किसका उपयोग करके किया जाता है - 
(a) Infra-red Rays/अवरक्त किरणों
(b) Ultrasonic Waves/अल्ट्रासोनिक किरणों
(c) Visible Light/ दृश्य प्रकाश
(d) X-Rays / एक्स-रे
Show Answer
Sol. CT scan or computed tomography are special x-rays tests that produce cross-sectional images of the body using x-rays and a computer.

Q11. In fiber-optics communication, the signal travels in the form of- 
फाइबर ऑप्टिक्स संचार में, सिग्नल किसके रूप में यात्रा करता है - 
(a) Lightwave / प्रकाश तरंग
(b) Radio wave/ रेडियो तरंग
(c) Microwave/ माइक्रो तंरग
(d) Electric wave /विद्युत तरंग
Show Answer
Sol. Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fibre.

Q12. 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 कोई नहीं
Show Answer
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.

Q13. 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
Show Answer
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.

Q14. Decibel is a –
डेसीबेल क्या है?
(a)musical note / संगीत नोट
(b)musical instrument / संगीत वाद्ययंत्र
(c)unit of intensity of sound / ध्वनि की तीव्रता की इकाई
(d)unit of elasticity / लोच की इकाई
Show Answer
Sol. The decibel ( dB) is used to measure sound level.

Q15. FM broadcasting service uses the range of frequency bands between –
एफएम प्रसारण सेवा किस बैंड आवृत्ति की सीमा का उपयोग करता है?
(a) 109-139 MHz / 109-139 मेगाहर्ट्ज
(b) 54-75 MHz / 54-75 मेगाहट्र्ज
(c) 76-87 MHz / 76-87 मेगाहर्ट्ज
(d) 88-108 MHz / 88-108 मेगाहट्र्ज
Show Answer
Sol.  FM broadcasting service uses the range of frequency bands between 88 to 108 MHz. There is a number of band allocation used around the globe:
1. 87.5 – 108 MHz: - It is the “standard” VHF FM band. The one Which is most widely used around the globe.
2. 76-90 MHz- This VHF FM band is used in Japan.
3. 65.8 – 74.0 MHz- This VHF FM band is known as the OIRT band. It was used in Eastern Europe although few other countries such as Russia, Ukraine also use it. 



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