# Physics [Light] Questions for Railway ALP Stage-II Exam : 4th December 2018

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Q1. 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
Ans.(b)
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.

Q2. 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

Ans.(a)
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.

Q3. 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

Ans.(c)
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.

Q4. 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

Ans.(d)
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.

Q5. 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

Ans.(b)
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.

Q6. The speed of light will be minimum while passing through-
किससे गुजरते समय प्रकाश की गति न्यूनतम होती है-
(a) Glass / कांच
(b) Vacuum / शून्यक
(c) Water / पानी
(d) Air / हवा

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.

Q7. Waves used for telecommunication are-
दूरसंचार के लिए किस प्रकार की तरंगों का उपयोग किया जाता हैं –
(a) Visible light /दृश्य प्रकाश
(b) Infrared/इन्फ्रारेड
(c) Ultraviolet/पराबैंगनी
(d) Microwave/माइक्रो तंरग
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.

Q8. Light from the Sun reaches Earth in about:
सूर्य से प्रकाश पृथ्वी पर कितनी देर में पहुंचता है:
(a) 2 minutes / मिनट
(b) 4 minutes  / मिनट
(c) 8 minutes / मिनट
(d) 16 minutes / मिनट
Ans.(c)
Sol. The sunlight takes about 500 second or 8.5 minutes to reach to the earth.

Q9. When light waves pass from air to glass the variable affected are-
जब प्रकाश तरंगों को हवा से कांच तक पहुंचा जाता है तो ______ 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
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.

Q10. 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 सा ऊर्जा रूपांतरण होता है?
(a) Light to chemical energy  / प्रकाश से रासायनिक ऊर्जा
(b) Light to thermal energy / प्रकाश से तापीय ऊर्जा
(c) Thermal to biochemical energy / थर्मल से जैव रासायनिक ऊर्जा
(d) Heat to kinetic energy / ऊष्मा से गतिशील ऊर्जा
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.
6CO_2+6H_2 O□(Chlrophyl  C_6 H_12 O_6+6O_2 )
Where CO_2 = Carbon dioxide
H_2 O=Water
C_6 H_12 O_6=Glucose
O_6=Oxygen

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