Physics [Light] Questions for Railway ALP Stage-II Exam : 10th December 2018

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Q1. A concave lens always forms an image which is
एक अवतल लेंस हमेशा कैसी छवि बनाता है?
(a) real and erect / वास्तविक और सीधी
(b) virtual and erect/ आभासी और सीधी
(c) real and inverted/ वास्तविक और उल्टी
(d) virtual and inverted/ आभासी और उल्टी
Show Answer
Sol. Concave lens will always form virtual, erect and diminished images. A virtual image larger than the object can be produced by a concave mirror.

Q2. The scientist who first sent electromagnetic waves to distant place is
वैज्ञानिक जिसने पहले विद्युत चुम्बकीय तरंगों को दूरस्थ स्थान पर भेजा था?
(a) James Clerk Maxwell/ जेम्स क्लर्क मैक्सवेल
(b) Heinrich Hertz/ हेनरिक हर्ट्ज
(c) Thomas Alva Edison/ थॉमस अल्वा एडीसन
(d) John Logie Baird / जॉन लॉजी बैरर्ड

Show Answer
Sol. The German physicist Heinrich Hertz is widely known for being one of the first scientists to broadcast and receive electromagnetic waves, but is also important for his contributions to the field of optics. Most notably, Hertz was the first investigator ever to observe the phenomenon that would eventually come to be known as the photoelectric effect.

Q3. Focal length of plane mirror is
समतल दर्पण की फोकल लंबाई-
(a) At infinity / अनंत पर
(b) Zero /शून्य
(c)Negative / नकारात्मक
(d) None of these / इनमें से कोई नहीं

Show Answer
Sol. A  plane mirror can be considered to be the limit of either a concave or a convex spherical curved mirror as the radius, and therefore the focal length, becomes infinite.

Q4. The part of the eye having the larges refractive index is
आंख का हिस्सा जिस का अपवर्तक सूचकांक सबसे बड़ा है?
(a) cornea/ कॉर्निया
(b) aqueous humor/ नेत्रोद
(c) lens/ लेंस
(d) vitreous humor/ नेत्रकाचाभ द्रव

Show Answer
Sol. The part of the eye having the largest refractive index is lens. It is located directly behind the iris (the coloured part of the eye) and the pupil. Its function is to focuses light on the retina.

Q5. A soap bubble shows colours when illuminated with white light. This is due to
एक साबुन का बुलबुला सफ़ेद रौशनी के साथ प्रबुद्ध होने पर रंग दिखाता है. यह किस वजह से होता है? 
(a) diffraction / विवर्तन
(b) polarization/ ध्रुवीकरण
(c) interference / व्यतिकरण
(d) reflection/ परावर्तन

Show Answer
Sol. Interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. A soap bubble shows colours when illuminated with white light is an example of  interference.

Q6. When a person walking in bright sunlight enters a dark room, he is not able to see clearly for a little while because
जब उज्ज्वल सूरज की रोशनी में चलने वाला व्यक्ति अंधेरे कमरे में प्रवेश करता है, तो वह थोड़ी देर के लिए स्पष्ट रूप से देखने में सक्षम नहीं होता है क्योंकि-
(a) the eye muscles cannot immediately adjust the focal length of the eye lens / ख की मांसपेशियां तुरंत आंखों के लेंस की फोकल लंबाई समायोजित नहीं कर पाती
(b) the retina retains the bright images for something and becomes momentarily insensitive / रेटिना कुछ चमकदार छवियों को रखता है और क्षणिक रूप से असंवेदनशील हो जाता है
(c) the iris is unable to contract the pupil immediately/ ईरिस तुरंत पुतली को अनुबंध करने में असमर्थ है
(d) the iris is unable to dilate the pupil immediately /ईरिस तुरंत पुतली को फैलाने में असमर्थ है

Show Answer
Sol. When a person walking in bright sunlight enters a dark room, he is not able to see clearly for a little while because the iris is unable to dilate the pupil immediately.

Q7. Spectacles used for viewing 3D films have 
3 डी फिल्मों को देखने के लिए इस्तेमाल किए गए चश्मे हैं
(a) bifocal lens / बाइफोकल लेंस
(b) convex lens/ उत्तल लेंस
(c) concave lens/ अवतल लेंस
(d) polaroids / पोलराइड
Show Answer
Sol. Polarized sunglasses provide superior glare protection .Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing also used as Spectacles used for viewing 3D films.

Q8. Which one of the following wavelengths of light is most effective in photosynthesis?
प्रकाश संश्लेषण में प्रकाश की निम्न तरंग दैर्ध्य में से कौन सा सबसे प्रभावी है?
(a) Blue/नीला
(b) Green/हरा
(c) Orange/ नारंगी
(d) Yellow/पीला
Show Answer
Sol. Red and blue wavelengths of light are the most effective in photosynthesis because they have exactly the right amount of energy to energize, or excite, chlorophyll electrons and boost them out of their orbits to a higher energy level.

Q9. According to the theory of relativity, which of the following always remains constant?
सापेक्षता के सिद्धांत के अनुसार, निम्नलिखित में से कौन सा स्थिर रहता है?
(a) Length of an object / किसी वस्तु की लंबाई
(b) Time/समय
(c) Space/ जगह
(d) Velocity of light/ प्रकाश की वेग
Show Answer
Sol. Theory of special relativity, determined that the laws of physics are the same for all non-accelerating observers, and he showed that the speed of light within a vacuum is the same no matter the speed at which an observer travels.

Q10.      A mirage occurs because of
मृगतृष्णा किस के कारण होता है?
(a) reflection by hot ground / गर्म जमीन से प्रतिबिंब
(b) total internal reflection by layers of air/ हवा की परतों द्वारा कुल आंतरिक प्रतिबिंब
(c) interference of light/ प्रकाश की हस्तक्षेप
(d) diffraction of light/ प्रकाश का विवर्तन
Show Answer
Sol. Its formation is a result of the refraction and the total internal reflection of light in the air. To investigate the formation of a mirage, we firstly need to understand why light is refracted in the air. Regions of air at different temperatures have different refractive indexes, just like many different mediums.

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