Physics Questions for Railway & SSC CGL Exam 2018 : 18th May

LIGHT:

Dear Students,

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 months 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. When light passes from one medium to another medium, which one of the followings does not change: 
जब प्रकाश एक माध्यम से दूसरे माध्यम में गुजरता है, तो निम्नलिखित में से क्या परिवर्तित नहीं होता है:
(a) Intensity/ गहनता
(b) Velocity/ गति
(c) Wavelength/ तरंग दैर्ध्य
(d) Frequency/ आवृत्ति
Show Answer
Ans.(d)
Sol. When light passes from air to glass or one medium to another, then the frequency of the light remains constant but wavelength and velocity are changed.

Q2. The visible range of solar radiation is- 
सौर विकिरण की दृश्य सीमा है
(a) 100-400 nm
(b) 400-700 nm
(c) 740-10000 nm
(d) None of the above/ उपरोक्त में से कोई नहीं
Show Answer
Ans.(b)
Sol. The electromagnetic spectrum encompasses all type of radiations. The part of the spectrum that reaches earth from the sun is between 100 nm to 10^6 nm. This band is broken into three ranges – Infrared (above 700 nm), Visible (400 to 700 nm), Ultraviolet (below 400 nm).

Q3. Total internal reflection can take place when light travels from: 
कुल आंतरिक प्रतिबिंब तब प्रभाव में आता है जब प्रकाश ___ में गुजरता है.
(a) Diamond to glass / हीरे से ग्लास
(b) Water to glass/पानी से ग्लास
(c) Air to water/ हवा से पानी
(d) Air to glass/ हवा से ग्लास
Show Answer
Ans.(a)
Sol.  Total internal reflection takes place when a ray of light is travelling from denser to thinner medium and angle of incidence is greater than the critical angle, the ray is completely reflected from surface and meet each other as if the surface is a mirror. So according to options, the situation of option (a) is correct where total internal reflection takes place, it is because diamond is denser than glass.

Q4. Human eye is most sensitive to visible light of the wavelength 
मानव नेत्र कितने तरंगदैर्ध्य के दृश्य प्रकाश के प्रति सबसे अधिक संवेदनशील है:
(a) 605nm
(b) 555nm
(c) 450nm
(d) 750nm
Show Answer
Ans.(b)
Sol. Under daylight conditions, the average normal sighted human eye is most sensitive at a wavelength of 555 nm.

Q5. The nature of radiation of light is-
प्रकाश की विकिरण की प्रकृति है- 
(a) Like wave / तरंगीय
(b) Like particle/  कणीय
(c) Like both of wave and particle /तरंगीय और कणीय दोनों
(d) Like neither of wave nor of particle/ना ही तरंगीय और न कणीय
Show Answer
Ans.(c)
Sol. The light has a dual nature, sometimes it behaves only as wave and sometimes as light. In the later part of the 19th century and in the beginning of 20th century, it was realized that black body radiation and the photelectric effect can be understood only on the basis of particle model of light. Some experiments require light to be a wave, while others require light to be a particle. This led to the acceptance of dual nature of light.


Q6. Light appears to travel in a straight line because- 
प्रकाश एक सीधी रेखा में प्रवाह करता प्रतीत होता है क्योंकि-
(a) It consists of small particles./ इसमें छोटे कण होते हैं
(b) The velocity of light is very large. / प्रकाश का गति बहुत अधिक है
(c) The wavelength of light is very small. / प्रकाश का तरंगदैर्ध्य बहुत कम है
(d) Light is reflected by the surroundings./ प्रकाश वातावरण द्वारा परिलक्षित होता है
Show Answer
Ans.(c)
Sol. Due to its very small wavelength, the light appears to travel in a straight line.


Q7. Which of the following statement is true? 
निम्नलिखित में से कौन सा कथन सत्य है?
(a) The light has a greater velocity. / प्रकाश का गति अधिक है
(b) The sound has the greatest velocity. / ध्वनि का गति सबसे अधिक है
(c) Celestial objects have the greatest velocity. / आकाशीय वस्तुओं में सबसे अधिक गति होता है
(d) Rocket has the greatest velocity. / रॉकेट का गति सबसे अधिक है
Show Answer
Ans.(a)
Sol. The speed of light in a vacuum is 3.00 x 10^8 m/s, while the speed of sound in vacuum is zero and in air is 343 m/sec. The speed of light in glass is 2,0 × 10^8 m/s. The velocity of light always greater than the velocity of sound. The velocity of celestial objects and the rockets in quite low than the velocity of light.

Q8. The speed of light in vacuum is nearly- 
शून्यक में प्रकाश की गति लगभग है-
(a) 3 × 10^10 metres/sec / मीटर / सेकंड
(b) 3× 10^8 metres/sec / मीटर / सेकंड
(c) 3× 10^8 km/sec / किमी / सेकंड
(d) 3× 10^8 light years /प्रकाश वर्ष
Show Answer
Ans.(b)
Sol. The speed of light in a vacuum is 3.00 x 10^8 m/s, while the speed of sound in vacuum is zero and in air is 343 m/sec. The speed of light in glass is 2,0 × 10^8 m/s. The velocity of light always greater than the velocity of sound. The velocity of celestial objects and the rockets in quite low than the velocity of light.

Q9 . Which one of the following phenomenon is used in optical fibres? 
निम्नलिखित में से कौन सा तथ्य ऑप्टिकल फाइबर में उपयोग किया जाता है?
(a) Interference  / व्यतिकरण
(b) Refraction / अपवर्तन
(c) Total internal reflection / कुल आंतरिक प्रतिबिंब
(d) Polarisation/ ध्रुवीकरण
Show Answer
Ans.(c)
Sol. The optical fibre is a very thin strand of glass or plastic cable for transmitting light from one point to another. They work on he principle of total internal reflection. There is no loss of signal through an optical fibre.


Q10. Velocity of light is maximum in- 
प्रकाश की गति अधिकतम है-
(a) Diamond /हीरा
(b) Water /पानी
(c) Vacuum /शुन्यक
(d) Hydrogen /हाइड्रोजन
Show Answer
Ans.(c)
Sol. The speed of light in vacuum is maximum (c = 3 × 10^8  ms^(-1)). The speed of light decreases gradually in optically denser mediums like water or glass. It is least in diamond.

Q11. The speed of light will be minimum while passing through- 
किसके माध्यम से जाने के दौरान प्रकाश की गति न्यूनतम होगी-
(a) Glass /कांच
(b) Vacuum /शुन्यक
(c) Water /पानी
(d) Air /हवा
Show Answer
Ans.(a)
Sol. Any of the object or material which has the highest refractive index has the minimum speed of light. The glass has the highest refractive index among other like, vacuum, water and air.

Q12. Waves used for telecommunication are- 
दूरसंचार के लिए उपयोग की जाने वाली तरंगे हैं
(a) Visible light / दृश्य प्रकाश
(b) Infrared / इन्फ्रारेड
(c) Ultraviolet / पराबैंगनी
(d) Microwave/ माइक्रो तंरग
Show Answer
Ans.(d)
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.

Q13. Light from the Sun reaches Earth in about: 
सूर्य से प्रकाश पृथ्वी पर कितने समय पहुंचता है-
(a) 2 minutes / मिनट
(b) 4 minutes / मिनट
(c) 8 minutes / मिनट
(d) 16 minutes / मिनट
Show Answer
Ans.(c)
Sol. The sunlight takes about 500 second or 8.5 minutes to reach to the earth.

Q14. When light waves pass from air to glass the variable affected are-
जब प्रकाश तरंगें हवा से ग्लास में जाती हैं तो कौन से चर प्रभावित होते हैं- 
(a) Wavelength, frequency and velocity/ तरंगदैर्ध्य, आवृत्ति और वेग
(b) Velocity and frequency / वेग और आवृत्ति
(c) Wavelength and frequency / तरंगदैर्ध्य और आवृत्ति
(d) Wavelength and velocity / तरंगदैर्ध्य और वेग
Show Answer
Ans.(d)
Sol. When light passes from air to glass or one medium to another, then the frequency of the light remains constant but wavelength and velocity are changed.


Q15. Which one of the following energy conversion takes place in carrying out the process of photosynthesis? 
प्रकाश संश्लेषण की प्रक्रिया को पूरा करने में निम्नलिखित में से कौन सी ऊर्जा रूपांतरण होती है?
(a) Light to chemical energy / प्रकाश से रासायनिक ऊर्जा
(b) Light to thermal energy / प्रकाश से तापीय ऊर्जा
(c) Thermal to biochemical energy / तापीय से जैव रासायनिक ऊर्जा के लिए थर्मल
(d) Heat to kinetic energy/ ऊष्मा से गतिज ऊर्जा
Show Answer
Ans.(a)
Sol. Photosynthesis is the process used by plants to convert light energy into chemical energy. Photosynthesis can be represented by using following chemical equation. 
6CO₂+6H₂O□(Chlorophyll) ---> C₆H₁₂O₆+6O₂  
Where CO₂ = Carbon dioxide 
H₂O=Water 
C₆H₁₂O₆=Glucose 
O₆=Oxygen 


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