Physics [Light] Quiz For ALP Stage-II Quiz Exam : 10th January

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Q1. The critical angle for light passing from glass into air is minimum for- 
ग्लास से वायु में गुजरने पर प्रकाश का क्रांतिक कोण किसके लिए न्यूनतम होता है? 
(a) Red light /लाल प्रकाश
(b) Yellow light /पीला प्रकाश
(c) Green light /हरा प्रकाश
(d) Violet light / बैंगनी प्रकाश

Show Answer
Sol. Critical angle will be directly proportional to velocity of particular color of light (Sinc directly proportional to v), which is minimum in the case of violet color. 

Q2. When the length of the tube of a microscope is increased, its magnifying power-  
जब एक माइक्रोस्कोप की ट्यूब की लंबाई बढ़ जाती है, तो इसकी आवर्धन शक्ति-
(a) Decreases /घट जाती है
(b) Increases/ बढ़ जाती है
(c) Remains constant /समान रहती है
(d) None of the above /इनमें से कोई नहीं

Show Answer
Sol. Magnifying power is directly proportional to the length of tube,
Magnifying power( M )= L/Fo (1+D/fe), Increasing the length of the tube will increase the magnifying power

Q3. The objective in a reflecting telescope is-  
एक परावर्तित दूरबीन में दर्पण किस प्रकार का होता है?
(a) Concave mirror / अवतल दर्पण
(b) Convex mirror / उत्तल दर्पण
(c) Prism / प्रिज्म
(d) Concavo-Convex lens / अवतल- उत्तल लेंस

Show Answer
Sol. Concave mirrors are used as objective in reflecting telescopes. 

Q4. A beam of electrons is used in Young’s double-slit experiment. If the speed of electrons is increased, the fringe-width will-  
इलेक्ट्रॉनों की एक बीम का उपयोग यंग के डबल-स्लिट प्रयोग में किया जाता है। यदि इलेक्ट्रॉनों की गति बढ़ जाती है, तो हाशिये-चौड़ाई –
(a) Increase /बढ़ जाएगी
(b) Decrease /घट जाएगी
(c) Remain same /समान रहेगी
(d) Fringe will not be seen / फ्रिंज नहीं दिखेगा

Show Answer

Sol. The fringe width will decrease. As λ = h/mv, if v will increase then according λ will decrease. Now fringe width = λD/d, hence it will also decrease.

Q5. Both light and sound have wave character, yet diffraction is much harder to observe in light, because- 
 प्रकाश और ध्वनि दोनों का तरंग चरित्र होता है, फिर भी प्रकाश में निरीक्षण करने के लिए विवर्तन बहुत कठिन होता है, क्योंकि
(a) Light can travel in vacuum / प्रकाश शून्यक में यात्रा कर सकता है
(b) Light waves are transverse / प्रकाश तरंगें अनुप्रस्थ होती हैं
(c) Speed of light is very high / प्रकाश की गति बहुत अधिक है
(d) Wave length of light is rather small / प्रकाश की तरंग लंबाई कम होती है

Show Answer
Sol. Due to very small wavelength of light, it is harder to observe diffraction of light in comparison to sound waves. Sin θ = λ/d hence λ is very less for light. 

Q6. Equation E = p.c. is valid for-  
समीकरण E = p.c. किस के लिए मान्य है-
(a) Both electron and Photon / इलेक्ट्रॉन और फोटॉन दोनों
(b) Electron only / केवल इलेक्ट्रॉन
(c) Photon only / केवल फोटॉन
(d) Neither electron nor photon / न तो इलेक्ट्रॉन और न ही फोटॉन

Show Answer
Sol. The equation E = p.c. is valid for particles with zero rest mass, which is valid for photons but not for electron

Q7. When beams of red, blue and green lights fall on the same spot, the colour of the light becomes-  
जब लाल, नीली और हरी प्रकाश किरणें एक ही स्थान पर पड़ती हैं, तो प्रकाश का रंग _______ हो जाता है-
(a) violet /बैंगनी
(b) red /लाल
(c) yellow /पीला
(d) white /सफ़ेद
Show Answer
Sol. When beams of red, blue and green lights fall on the same spot, the colour of the light becomes white .

Q8. In fiber-optics, the signal source is- 
फाइबर-ऑप्टिक्स में, सिग्नल स्रोत क्या है?
(a) Light waves / प्रकाश तरंगे
(b) Sound waves / ध्वनि तरंगे
(c) α-rays / अल्फा-रे
(d) Cosmic rays / ब्रह्मांडीय किरणों

Show Answer
Sol. Fibre optics is the science of transmitting data, voice, and image by the passage of light through thin, transparent fibres.

Q9. Sound wave travel fastest in-  
ध्वनि तरंग सबसे तेज किसमें यात्रा करती है?
(a) solids / ठोस
(b) liquids / तरल पदार्थ
(c) gases / गैसों
(d) vacuum / शून्यक

Show Answer
Sol. Speed of sound varies from substance to substance. Sound travels most slowly in gases; it travel faster in liquids and faster still in solids. For example, sound travels at 343 m/s in air; it travels at 1484 m/s in water (4.3 times as fast as in air) and at 5120 m/s in iron. 

Q10. The power of a lens is measured in-  
एक लेंस की शक्ति को किसमें मापा जाता है?
(a) dioptre / डायोपप्टर
(b) aeon / एयॉन
(c) lumen / लुमेन
(d) candela / कैन्डेला

Show Answer
Sol. Power of lens is the ability of the lens to converge the rays of light falling on it. In other words, the power of a lens is the reciprocal of its focal length in metres. It is measured in dioptre. 1 dioptre is the power of lens whose focal length is 1 metre.

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