RRB JE Exam: Physics (Light) Quiz | 11th March

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Q1. A cut diamond sparkles because of its
एक तराशा हुआ हीरा किस की वजह से चमकता है-
(a) hardness / कठोरता
(b) high refractive index / उच्च अपवर्तक सूचकांक
(c) emission of light by the diamond / हीरे द्वारा प्रकाश का उत्सर्जन
(d) absorption of light by the diamond / हीरे द्वारा प्रकाश का अवशोषण

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Ans.(b)
Sol. Diamonds have a very high refractive index (about 2.42 compared to about 1.5 for glass). The amount of light reflected at an air/other material interface is related to the refractive index charge at the interface and the bigger the refractive index change, the more light is reflected. Thus, diamond reflects large amount of light and therefore, sparkles more.


Q2. Butter paper is an example of …….. object.

बटर पेपर ________ ऑब्जेक्ट का एक उदाहरण है
(a) a transparent / पारदर्शक
(b) a translucent / पारदर्शी
(c) an opaque / अपारदर्शी
(d) a luminous / प्रकाशमान

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Ans.(b)
Sol. Butter paper is a translucent object as it allows light to pass through it partially, thus not providing clear vision. While, a transparent substance allows light to pass through it completely providing a clear vision. Whereas, an opaque substance is impenetrable to light. On the other hand, luminous objects emit their own light.


Q3. A vibrating body

एक कांपता हुआ शरीर
(a) will always produce sound / हमेशा ध्वनि उत्पन्न करेगा
(b) may or may not produce sound if the amplitude of vibration is low / कंपन का आयाम कम होने पर ध्वनि उत्पन्न कर भी सकता है और नहीं भी
(c) will produce sound which depends upon frequency / ध्वनि उत्पन्न करेगा जो आवृत्ति पर निर्भर करता है
(d) None of these /इनमें से कोई नहीं

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Ans.(c)
Sol. A vibrating body will produce sound which is dependent upon the frequency. Sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. Such sounds are called inaudible. On the higher side, sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear.

Q4. The special technique used in ships to calculate the depth of ocean beds is
महासागरों की गहराई की गणना के लिए जहाजों में प्रयुक्त विशेष तकनीक है
(a) LASER
(b) SONAR
(c) sonic boom / ध्वनि बूम
(d) reverberation/ प्रतिध्वनि

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Ans.(b)
Sol. SONAR or sound Navigation and Ranging is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. These also determine the time between the emission of sound pulse and its reception, the transducer can determine the range and orientation of the object. While, LASER is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Whereas, sonic boom is the sound associated with the shock waves created by an object travelling through the air faster than the speed of sound. On the other hand, reverberation is the prolongation of a sound.



Q5. The colour of the star is an indication of its
सितारे का रंग किसका संकेत है:
(a) Distance from earth / पृथ्वी से दूरी
(b) Temperature / तापमान
(c) Luminosity / चमक
(d) Distance from the sum / सूर्य से दूरी

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Ans.(b)
Sol. The colour of the star is an indication of its temperature according to Wein’s displacement law λ × T = B
Where λ = Wavelength
T = Temperature and
B = Constant whose value is


Q6. Sound travels in the form of
ध्वनि ____ के रूप में यात्रा करता है
(a) transverse waves / अनुप्रस्थ तरंग
(b) longitudinal waves / अनुदैर्ध्य तरंग
(c) stationary waves / स्थिर तरंग
(d) none of the above / उपरोक्त में से कोई नहीं

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Ans.(b)
Sol. Sound travels in the form of longitudinal waves. These waves travel in the form of compressions and rarefactions.


Q7. The mirror used by a dentist to examine the teeth of patients is

दंत चिकित्सक द्वारा रोगियों के दांतों की जांच करने के लिए इस्तेमाल किया जाने वाला दर्पण है
(a) Concave/ अवतल
(b) Convex/ उत्तल
(c) Plane/समतल
(d) Cylindrical / बेलनाकार

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Ans.(a)
Sol. The mirror by a dentists to examine the teeth of patients is concave as concave mirror given upright and magnified image of the object. While, image formed by a convex mirror is upright but diminished. On the other hand, image formed by plane mirror is of the same size as the object.


Q8. Sound above what level (in decibel) is considered hazardous noise pollution?
किस स्तर (डेसीबल में) के ऊपर की ध्वनि खतरनाक ध्वनि प्रदूषण माना जाता है?
(a) 30 dB
(b) 40 dB
(c) 60 dB
(d) 80 dB

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Ans.(d)
Sol. A sound’s loudness is measured in decibels (dB). Normal conversation is 60dB and more then 80dB are harmful, depending on how long and how often one is exposed to them.


Q9. Dispersion process forms spectrum due to white light falling on a prism. The light wave with shortest wavelength

प्रिज़्म पर सफेद प्रकाश गिरने के कारण प्रकीर्णन की प्रक्रिया स्पेक्ट्रम बनाती है। सबसे छोटी तरंग दैर्ध्य वाली प्रकाश की किरण-
(a) Refracts the most / सबसे अधिक अपवर्तित होती है
(b) Does not change the path/ अपना मार्ग नहीं बदलता है
(c) Refracts the least/ सबसे कम अपवर्तित होती है
(d) Is reflected by the side of the prism / प्रिज़्म के किनारों द्वारा परावर्तित होती है

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Ans.(a)
Sol. The light wave with shortest wavelength i.e. violet refracts the most.



Q10.In a three pin plug, the longest pin should be connected to
एक तीन पिन वाले प्लग में, सबसे लम्बा पिन ____ से जुड़ा होना चाहिए
(a) ground terminal / ग्राउंड टर्मिनल
(b) live terminal / लाइव टर्मिनल
(c) neutral terminal/ न्यूट्रल टर्मिनल
(d) any terminal / किसी भी टर्मिनल

Show Answer
Ans.(a)
Sol. In a three pin plug longest pin should be connected to ground terminal. Ground pin is the largest to supply the additional voltage that can give electric shock. And being the longest it can touch before live and neutral terminal.

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