Physics [Light] Questions for Railway ALP Stage-II Exam : 26th November 2018

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Q1. On a rainy day, small oily films on water show brilliant colours. This is due to
बरसात के दिन, पानी पर छोटी तेल की परत शानदार रंग दिखाती हैं. इसका कारण है 
(a) Scattering / प्रकाश प्रकीर्णन
(b) Interference/ प्रकाश का व्यतिकरण
(c) Refraction / अपवर्तन
(d) Polarization/ ध्रुवीकरण
Show Answer
Sol. When petrol is dropped on the road during a rainy day, a thin layer of oil will appear on the water surface. Both the top and bottom surfaces of this oil film can reflect light. If the path difference between two light rays is an integral times of the wavelength, there will be constructive interference.

Q2. Rainbow formation is due to
इंद्रधनुष किस के कारण बनता है?
(a) Absorption of sunlight by water droplets/ पानी की बूंदों द्वारा सूरज की रोशनी के अवशोषण के कारण
(b) Diffusion of sunlight through water droplets/ पानी की बूंदों के माध्यम से सूरज की रोशनी का विसरण
(c) Ionization of water droplets/ पानी की बूंदों का आयनीकरण
(d) Reflection, refraction and dispersion of light/ प्रतिबिंब, अपवर्तन और प्रकाश का फैलाव

Show Answer
Sol. A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Q3. Stars appears to move from east to west because
सितारे पूर्व से पश्चिम की ओर जाते हुए प्रतीत होते हैं क्योंकि
(a) all stars move from east to west/ सभी सितारे पूर्व से पश्चिम की ओर जाते हैं
(b) the earth rotates from west to east/ पृथ्वी पश्चिम से पूर्व की ओर घूमती है
(c) the earth rotates from east to west/ पृथ्वी पूर्व से पश्चिम की ओर घूमती है
(d) the background of the stars moves from west to east/ सितारों का बैकग्राउंड पश्चिम से पूर्व की ओर जाता है

Show Answer
Sol. Earth rotates or spins toward the east, and that’s why the Sun, Moon, planets, and stars all rise in the east and make their way westward across the sky.

Q4. Which of the following is not caused by atmosphere refraction of light?
निम्नलिखित में से क्या प्रकाश की वायुमंडलीय अपवर्तन के कारण नहीं होता है?
(a) Twinkling of stars at night/ रात में सितारों का टिमटिमाना
(b) Sun appearing higher in the sky than it is actually/ सूर्य आकाश में वास्तव से अधिक ऊँचा दिखाई देता है
(c) Sun becoming visible two or three minutes before actual sunrise/ सूर्य का सूर्योदय से दो या तीन मिनट पहले दिखाई देना
(d) Sun appearing red at sunset/ सूर्य का सूर्यास्त के समय लाल दिखाई देना

Show Answer
Sol. Twinkling of stars at night , Sun appearing higher in the sky than it is actually and Sun becoming visible two or three minutes before actual sunrise are caused by atmosphere refraction of light.

Q5. One can distinguish a telescope from a microscope by observing
एक टेलीस्कोप और एक माइक्रोस्कोप में अंतर कैसे पता चलेगा?
(a) length /लम्बाई
(b) colour /रंग
(c) size of the lens/ लेंस का आकार
(d) None of these/इनमें से कोई नहीं

Show Answer
Sol. Telescope and microscope are two different optical instruments to view the objects easily.
Telescope are used to view the distant objects while very near objects can be viewed by using the microscope. The simple microscope is used for observing magnified images of objects.
It consists of a converging lens of small focal length. Compound microscope is a combination of two convex lenses. The telescope is also a combination of two lenses which is used for observing distinct images of heavenly bodies like stars, planets etc.

Q6.The principle due to which circular patches of light is seen under a tree during day time, is similar to that of image formation by a
किस सिद्धांत के कारण दिन के दौरान एक पेड़ के नीचे प्रकाश के गोलाकार पैच को देखा जाता है, यह छवि निर्माण किस के समान होता है?
(a) concave lens/ अवतल लेंस
(b) pinhole/ पिनहोल
(c) photographic camera / फोटोग्राफिक कैमरा
(d) convex lens/ उत्तल लेंस

Show Answer
Sol. A pinhole camera is a simple camera without a lens and with a single small aperture, effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects, an inverted image on the opposite side of the box .This is similar to that principle due to which circular patches of light is seen under a tree during day time.

Q7. When a strong beam of light is passed through a colloidal solution, the light will
जब एक कोलाइडियल समाधान के माध्यम से प्रकाश की एक मजबूत बीम पारित की जाती है, तो प्रकाश क्या होगा-
(a) Be scattered / प्रकाश का प्रकीर्णन होगा
(b) Pass unchanged/ अपरिवर्तित निकल जाएगी
(c) Be absorbed/ अवशोषित हो जाएगी
(d) Be reflected/ प्रतिबिंबित हो जाएगी
Show Answer
Sol. When a beam of light is passed through a colloidal solution, then scattering of light is observed. This is known as the Tyndall effect. This scattering of light illuminates the path of the beam in the colloidal solution.

Q8. Mirage is an example of 
मृगतृष्णा किस का एक उदाहरण है?
(a) refraction of light only/ केवल प्रकाश की अपवर्तन
(b) total internal, reflection of light only/ कुल आंतरिक और केवल प्रकाश का प्रतिबिंब
(c) refraction and total internal reflection of light/ अपवर्तन और प्रकाश का कुल आंतरिक प्रतिबिंब
(d) dispersion of light only/ केवल प्रकाश का फैलाव
Show Answer
Sol. The angle of incidence i is smaller than the angle of refraction r. Total internal reflection occurs when the incident angle i is larger than the critical angle c. The path of light when a mirage happens Its formation is a result of the refraction and the total internal reflection of light in the air.

Q9. The phenomenon of light associated with the appearance of blue colour of the sky is
आकाश के नीले रंग की उपस्थिति से जुड़े प्रकाश की घटना को क्या कहा जाता है ?
(a) interference/ व्यतिकरण
(b) reflection/ प्रतिबिंब
(c) refraction/ अपवर्तन
(d) scattering /प्रकाश प्रकीर्णन
Show Answer
Sol. The phenomenon of light associated with the appearance of blue colour of the sky is scattering of light.
The sky appears blue because in the sun light, the blue colour of light is scattered maximum and this scattered blue light enters our eyes and therefore, the sky appears blue in appearance.

Q10. Lens in made up of
लेंस किस से बना होता है
(a) pyrex glass/ पाइरेक्स ग्लास
(b) flint glass/ फ्लिंट ग्लास
(c) ordinary glass/ साधारण ग्लास
(d) cobalt glass/ कोबाल्ट ग्लास
Show Answer
Sol. The Latin name for lentil is lens culinaris, and this is the origin of the modern word, “lens”. In addition to crown glass and flint glass, modern day lens makers use quartz crystals and acrylic plastic. These materials may be used in combination.

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