[Answerkey] CAPF-2013: Science, Physics, Chemistry, Biology, Space, IT related MCQs solved with explanation, reference

Science61 Comments

  1. Analysis- Science MCQs in CAPF 2013
  2. Physics internal breakup
    1. Optics related
    2. Electricity related
    3. Force/Motion
  3. Chemistry
  4. Botany related
  5. Sci-Tech
    1. Space related
    2. IT related

Analysis- Science MCQs in CAPF 2013

  1. Last year 16 questions, this year 20 questions out of 125.
  2. NESSOsat came in TheHindu in Feb’13.= hints us a timeframe that sci-tech related current affairs for one year (starting from January) should be prepared.
  3. Traditionally, in UPSC Exams, the Science related (Static) MCQ come mostly from Physics. Although in CSAT 2013 UPSC gave more focus to Biology related MCQs. but in CAPF 2013- UPSC has still followed the old tradition and focused on Physics.
  4. Majority of the questions can be solved through NCERT. And in order to raise difficulty level UPSC relied more on class 11-12 NCERTs but nonetheless same questions can also be solved through General studies manual. (meaning those from arts/commerce background- who find class-11-12 NCERTs difficult to understand- they were not at disadvantage as long as they revised GS Manual)
  5. Soapbubble, lotus leaf were trap questions.
  6. within science- majority from static (theory) portion, just like last year.
  7. last year they asked about Mars rover, this year they again asked about Mars rover.
  8. Last year they asked an easy question from computers (about wifi). This year, they repeated the same pattern by asking an easy question about Modem.
  9. last year they asked about television remote, this year- asked about television display technologies.
  10. unlike last year, no question on disease.

Science internal breakup



Polity14Covered. Click me
Geography+EnB+Agro14+8Covered. Click me
Economy+IR+PIN21+4+2Click ME
Science20Given in this article.
History22click me
Aptitude20to be released soon

Corrections, Additions post them in comments.

Physics internal breakup

Total Physics8

Optics related

Q1. Statement- I The mirror used in searchlight is parabolic.

Statement II- All the rays coming from the source at the focus of a parabolic mirror are reflected as an intense parallel beam.

  1. Both the statements are individually true and Statement II is the correct explanation of Statement I
  2. Both the statements are individually true but Statement II is not the correct explanation of Statement I
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true

Tata Macgrawhill General Studies Manual, Science section, Page 25

Another type of concave mirror is parabolic mirror. It reflects a parallel beam of constant intensity. Because of this property, parabolic mirrors are used in searchlight and headlamps of cars.

Hence both statements correct and II explains I. =>Answer (A)

Q2. Diamond Ring, God’s Eye and Baily’s Beads are the parts of phenomenon?

  1. Solar eclipse
  2. Aurora
  3. Lightning
  4. Solar storm

NASA: http://science1.nasa.gov/science-news/science-at-nasa/1999/ast05aug99_1/

On August 11, 1999, millions of people in the Northern Hemisphere will have one last chance in this millennium to marvel at a total solar eclipse.… some of Nature’s rarest wonders — “Bailey’s Beads,” the “Diamond Ring,” mysterious shadow bands, and, of course, the Sun’s ephemeral corona.

Hence answer (A)

Q3. Formation of colors in soapbubble due to

  1. dispersion of light
  2. interference of light
  3. diffraction of light
  4. polarization of light

Tata Macgrawhill General Studies Manual, General Science section, Page29

Beautiful colors seen in soap bubbles and oil films on water are produced due to the interference of white light reflected by these surfaces.

Conceptual Physics, 10/E By Hewitt, page 568

We’ve all noticed the beautiful spectrum of colors reflected from soap bubble or from gasoline on a wet street. These colors are produced by the interference of light waves. This phenomenon is often called iridescence and is observed in transparent films.

The Magical Effects of Color By Joen Wolfrom, Page 42-43

Some glorious iridescent colorations are formed by nature thru process called constructive and destructive interference. This type of iridescence relates to color produced from filmy matter such as oil slicks and soap bubbles…..The colors we see in soap bubbles are created similarly, with the film of bubble causing interference as the waves hit the surface.

Hence answer (B)

Electricity related

Q1. Transformer is used to

  1. convert low a.c. voltage to high voltage
  2. convert high a.c. voltage to low voltage
  3. convert direct current to alternating current
  4. regulate the fluctuation of voltage

select answer

  1. 1 and 3 only
  2. 3 and 4
  3. 1 and 2 only
  4. 1, 2 and 3

Tata Macgrawhill General Studies Manual, General Science section, Page 35

  • Electrical energy can be easily and cheaply changed from one voltage to another by a transformer without much loss of energy.
  • At power station electricity is generated at 11 kV and then stepped up to 132 kv for transmission to main substations. =>statement 1 correct
  • At main substation, voltage is stepped down to 33kv.=>statement 2 correct.
  • An inverter is a device which converts DC to AC. =>Statement 3 is incorrect.

Eliminate all choices involving 3

  1. 1 and 3 only
  2. 3 and 4
  3. 1 and 2 only
  4. 1, 2 and 3

Thus we are left with answer C.

Q2. The filament of electric bulb is generally made of tungsten because

  1. tungsten is cheap
  2. durability of tungsten is high
  3. light-emitting power of tungsten is high
  4. melting point of tungsten is high

NCERT Class 10, ch12, page218

A strong metal with high melting point such as tungsten (melting point 3380°C) is used for making bulb filaments.

Tata Macgrawhill General Studies Manual, General Science section, Page 36

Tungsten is used because it has high melting point of 3600 Degree Celsius. Either way: answer (D)

Q3. Advanced sunrise and delayed sun- set found in the sky are due to the phenomenon of  

  1. diffraction of sunlight
  2. refraction of sunlight
  3. scattering of sunlight
  4. total internal reflection of sun-light

NCERT Class 12 Physics, Chapter 9, Page 318

Refraction of light through the atmosphere is responsible for many interesting phenomena. For example, the sun is visible a little before the actual sunrise and until a little after the actual sunset due to refraction of light through the atmosphere

Tata Macgrawhill General Studies Manual, General Science section, Page 25

It Is due to refraction produced by the earth’s atmosphere, that the sun is visible for several minutes after it has set below the horizon.

Myth Information: More Than 590 Popular Misconceptions, Fallacies by By J. Allen Varasdi, Page 187

All sunrises and sunsets are an illution created by refraction of the light from Sun as it enters the thicker atmospere of the earth.
The effect of this refraction, at the equator, is that the Sun appears to rise about two minutes earlier than it otherwise would, if its rays were not bent, and it delays the image of the sunset also about two minutes.
Hence answer (B)
by the way, LucentGK has given wrong information: it says total internal refraction. But since NCERT says refraction of light hence I go with B, because in UPSC- NCERT gets precedence over other sources.

Q4. What is the correct sequence of conductivity when arranged in ascending order?

  1. Metals, semiconductors, insulators
  2. Insulators, metals, semi-conductors
  3. Semiconductors, metals, insulators
  4. Insulators, semiconductors, metals

Tata Macgrawhill General Studies Manual, General Science section, Page 34

Nearly all metals are good conductors and most non-metals are poor conductors or insulators…..certain materials have electrical resistivity intermediate between conductors and insulators. These material are termed as semiconductors. =>Thus order will be Insulator, semiconductor, metal.

another source,

Introduction to Semiconductor Physics  By Holger T. Grahn, Page 2

The term semiconductor has been used to denote materials with a much higher conductivity than insulators but a much lower conductivity than metals.

Hence correct sequence: insulator<<semiconductor<<metal. Answer (D)


Q1. Geostationary satellite completes its one revolution around the earth in

  1. 90 minutes
  2. 24 hours
  3. 30 days
  4. 365 days

NCERT Class 11 Physics, Chapter 8 Page 197

Satellites in a circular orbits around the earth in the equatorial plane with T= 24 hours are called Geostationery Satellites. Clearly, since the earth rotates with the same period, the satellite would appear fixed from any point on earth.

Tata Macgrawhill General Studies Manual, Section: General Science: Page 11 talks about the same thing. Hence

Answer (B) 24 hours


Q1.Natural gas is a mixture of

  1. methane+high hydrocarbons
  2. butane+isobutane
  3. methane only
  4. methane, hydrogen,carbon monoxide

Debatable: A, C, D

Tata Macgrawhill General Studies Manual, Chemistry section, Page 255

Natural gas contains about 80% methane, 10% ethane and remaining 10% being higher gaseous hydrocarbons=>Hence answer A

Analytical Chemistry: By Dr. B. K. Sharma

Natural gas has two varieties:

DRYmethane, ethans, small amounts of carbon monoxide, carbon dioxide, H2, H2S,N2 and inert gases=> Answer D correct.
WETmethane and higher hydrocarbons=>Answer A correct.

Handbook of Industrial Hydrocarbon Processes  By James G. Speight, Page 134

DRYalmost pure methane. =>answer C
WetWet Natural gas=Methane + higher hydrocarbons=> Answer A

Britannica: http://www.britannica.com/EBchecked/topic/406163/natural-gas

natural gas, colourless, highly flammable gaseous hydrocarbon consisting primarily of methane and ethane…. Natural gas is often found dissolved in oil…. usually contains some light liquids such as propane and butane. For this reason associated gas is sometimes called “wet gas.” (and since Propane-Butane=higher hydrocarbons, hence answer A)

Q2.Diamond is a polymorph of graphite. Both contain carbon atoms. Diamond is obtained after applying

  1. very high pressure and low temperature
  2. very low pressure and high temperature
  3. very low pressure and low temperature
  4. very high pressure and high temperature

NCERT Class 10, Ch.4, Page 61

Diamonds can be synthesized by subjecting pure carbon to very high pressure and temperature. These synthetic diamonds are small but are otherwise indistinguishable from natural diamonds

Hence answer (D)

Q3. Which one among the following is not a form of carbon?

  1. Graphene
  2. Graphite
  3. Fullerene
  4. Quartz

NCERT Class 11 Physical geography, ch5, page 41. Quartz it is one of the most important components of sand and granite. It consists of silica. Hence answer (D)

by the way, What is Fullerene?

Ans. NCERT Class 10, Ch.4, Page 61

Fullerenes form another class of carbon allotropes. The first one to be identified was C-60 which has carbon atoms arranged in the shape of a football. Since this looked like the geodesic dome designed by the US architect Buckminster Fuller, the molecule was named fullerene.

Q4. Arsenic present in groundwater can be partially removed

  1. along with removal of iron by precipitation/coagulation method if iron is also present in the water
  2. on boiling even if iron is absent in the water
  3. on UV-treatment
  4. on filtration even if iron is absent in the water

Implementation of Arsenic Treatment Systems:  By Bryan Black, T. David Chinn, Samuel A. L. Perry Page 28

if dissolved iron is naturally present in source water, it can be oxidized to form a precipitate to absorb arsenic in the same manner as coagulant addition…

Advanced Processes for Simultaneous Arsenic and Manganese Removal Page 2

The steps to remove arsenic by precipitation are…Initiate precipitation by adding a coagulant or oxidizing dissolved iron naturally present in the source water.

Hence Answer (A)

Botany related

Q1. Statement I: When a piece of brick lying on grass for a number of days is removed, the covered part of the grass appears pale.

Statement II: Synthesis of chlorophyll, which gives green pigment, occurs in presence of sunlight.

  1. Both the statements are individually true and Statement II is the correct explanation of Statement I
  2. Both the statements are individually true but Statement II is not the correct explanation of Statement I
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true

Certificate Biology: Part II for Class X  By Dr. Rajendra Sharma. Page 67

Exposure to plant parts to light induces the formation of cholorphyll. In some cases, even roots, when exposed to Sunlight become green…lack of Sunlight impairs with Chlorophyll synthesis and the plants lose their green color.

Hence both statement correct and II explains I. Answer (A)

Another source: Advances in Chlorophyll Research and Application, Chapter 2, Page 272

…insufficient or low light intensity sunlight contributes to a loss of chlorophyll production.

Q2. Leaves of lotus and water lily are not easily wet because the leaves

  1. have surface uneven in micro-scale and water cannot come into contact with the depressed areas due to high surface tension
  2. contain an oily substance
  3. contain a greasy substance
  4. have surface too smooth to attract water

From IIT Kanpur website:


lotus leaf self-cleaning ability is due to the roughness of its surface at micro and nano level. The micro relief of plant surfaces, mainly caused by epicuticular wax crystalloids forming bumps, serves  different purposes and often causes effective water repellency.

From Beloit College, USA


Page 2-3

Each lotus leaf surface is covered with an array of tiny bupbs. This uneven surface is itself covered with waxy hydrophoci crystals. The two-tier roughness on leaf’s surface minimises the contact between the solid surface and waterdrops. You trap air below your drop so drop sits on the patchwork of solid

Imagine a fakir carpet- where water drop is the fakir sitting on a bed of nails. The drop sat atop the fakir carpet roll away easily.

Hence Answer (A)


Space related

Q1. Consider the following statements about NEOSSat launched by PSLV in February 2013

  1. It is the only space telescope dedicated to searching for asteroids that might have a threat to the earth.
  2. It was designed and developed by ISRO.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2

NEOSSat will be the only space telescope dedicated to searching for asteroids that might pose a threat to our planet.=1 is correct

It was designed by Canadians =>2 is incorrect

Hence answer (A) only 1

Ref. http://www.thehindu.com/news/national/neossat-to-be-launched-by-pslv-will-search-for-asteroids-heading-towards-earth/article4449684.ece

Q2. Which one among the following is not a Mars rover?

  1. Sojourner
  2. Opportunity
  3. Curiosity
  4. Apollo

let’s check

  1. sojourner is mars rover. http://www.nasa.gov/mission_pages/mars-pathfinder/
  2. Opportunity  is a mars rover. http://www.nasa.gov/mission_pages/mer/opportunity-update.html
  3. curiosity =mars rovers, keeps making news every now and then

Hence we are left with answer (D) Apollo

IT related

Q1. Which of the following is the correct chronological order of TV display technologies?

  1. CRT, Plasma, LED
  2. CRT, LED, Plasma
  3. LED, CRT, Plasma
  4. Plasma, LED, CRT

from the timeline given here


1897 – The first Cathode Ray Tube (CRT) was built by Karl Ferdinand Braun.

1964 – The first flat plasma display panel (PDP) was invented by Donald Bitzer, Gene Slottow and Robert Willson.

1977 – The first true all LED flat panel television TV screen was developed by J. P. Mitchell.

Hence answer A.

Q2. Which one among the following statements about ‘modem’ is correct?

  1. Modem is a software
  2. Modem helps in stabilizing the voltage
  3. Modem is an operating system
  4. Modem converts the analog signal into digital signal and vice versa

NIOS IT material, Chapter


A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.

Hence answer (D)

Q3. Electricity meter may be a/an

  1. mainframe computer
  2. microcomputer
  3. hybrid computer
  4. analog computer

Google patent says it is a micro computer
An electricity meter which, in one embodiment, includes a microcomputer coupled to both a liquid crystal display (LCD) and an optical port. The LCD includes an on board controller and an LCD random access memory (RAM).

Q4. ‘Turing machine’ serves as

  1. a machine to identify explosives
  2. an indicator to inform about forest fire
  3. an instrument for finding out gravitational constant
  4. a theoretical computing machine to act as an ideal model for mathematical calculation

Turing machine, hypothetical computing device introduced in 1936 by the English mathematician and logician Alan M. Turing.

Hence answer (D)

Ref. Britannica: http://www.britannica.com/EBchecked/topic/609750/Turing-machine

Any corrections/addition, post them in comments below.

Mrunal recommends

  1. (free) NCERT, NIOS, TN-Books
  2. Environment by ShankarIAS
  3. Indian Polity M.Laxmikanth (Hindi | English)
  4. Art & Culture by Nitin Singhania (Hindi | English)
  5. Spectrum: Modern History (Hindi | English)
  6. Bipin Chandra: Post Independence
  7. Fast-track to Arithmetic Rajesh Verma
  8. MK Pandey’s Analytical Reasoning
  9. Disha’s Topicwise Paperset (Hindi | English)
  10. School Atlas
  11. Mains: Language papers
  1. (free) NCERT, NIOS, TN-Books 4 History,Geo,Sci
  2. Indian Polity M.Laxmikanth (Hindi | English)
  3. Spectrum: Modern History (Hindi | English)
  4. Maths: Quantam CAT Sarvesh Kumar
  5. Objective General English SP Bakshi
  6. Word Power made Easy -Norman Lowe
  7. Topic wise Solved Paperset by Disha

So far 61 Comments posted

  1. vinay

    thank u bro…..

    1. rajendra maharia

      thank you very much sir

  2. chandan

    scattering of sunlite should be answer as lucent hindi page 292

    1. v verma

      ncert is more reliable source..

  3. A J S

    Natural Gas question: option (A) seems correct

    1. chandan

      correct bhai

      1. Prateek

        But natural gas consists of 95% methane! So i guess Methane should be the right answer…

  4. raj

    please clear my doubt on disqualification from house. please please

      1. H.s

        Analog Computer works on continuous range
        varied values of Physical quantities like
        Temperature, Speed, Voltage, Pressure etc. and
        generates approximate results.
        The Digital computer is designed with digital
        circuits in which there are two levels (logic 0
        logic 1) for an input and output signal. This
        computer is very much useful to solve complex
        problems in Engineering and Technology and
        hence it has increasing use in the field of
        research and data processing. If this digital
        computer is used for any type of application,
        it is called as General Purpose Computer and
        Special Purpose Computer when it is used for
        specific application/program.
        electric meter comes under the analog
        computer as quantity measured is continous in
        the form of analog signals.

      2. Jude_Prudence

        Q3. Electricity meter may be a/an

        mainframe computer
        hybrid computer
        analog computer

        pathetic loser type question. Don’t know if they themselves test run these questions

        Option 1: Main frame…obviously no

        Option 2:Yes possible, but it first takes analog data (obviously as AC current is analog) and then uses Analog to digital converter and runs test using ASIC..in short it can be considered as true. Most modern states have these “tamper” proof meters

        Option 3: YES! You remember the black ancient meters with Ferriwheel they are TRUE ANALOG computers Most old homes still have this. Some people use magnets to slow down the speed of the wheel

        Option 4: Yes, these are also there, but not in vogue in our country or not at least on large platform

        So, the question must have been: Which of these “CANNOT” be an electricity meter.

        1. Me (ok, you don’t believe me fine)
        2. naked science
        3.How stuff works

        Ab tou maan lo ki question idiotic hai or it’s incorrect.

  5. gauravsingh

    sir kindly prefer the economical solution than aptitude… i am fuly satisfied with all ue science answers…

    1. Mrunal

      yes Economy solution will be released soon.

  6. Vikram

    Electricity meters…….a few years back were used to be analog but nowdays new electricity meters are digital…this we can see in our houses..

  7. 27

    the question is what does natural gas contains mainly so methane which forms major part (80 percent)may be the answer methane only

    1. Dusky

      I too marked the same coz of similar thinking.. Mainly it consists of Methane only so it shud be the right ans.

      1. bharath ram

        i marked it as methane n hydro carbon…but answer is methane only..directly picked line from ncert

    2. gauravsingh

      there has a basic difrence beetween 80% n 100%…. 80% methene is corect but what abut remaining 20%.. ? its hydro carbon

    3. AKG47

      Bro. its 100% methane+higher hydrocarbons.. any AIEEE or IIT can answer this… without reading books

      1. Prateek

        It’s methane because according to many authors the main component of natural gas is methane… i.e 95%

        1. AKG47

          Methane only is wrong answer.. because in very less amount N.G. contains higher hydrocarbons..

  8. gauravsingh

    sir plz uplode the economical solution..i m egerly waiting 4 it

  9. vicky

    keeping an eye on google doodle also helps-Allan Turing

  10. vicky

    natural gas doesn’t contain co & Hydrogen

  11. girish

    I m gettng 110 marks..1st ppr…answers by prepare india….any hope for pet.???

  12. girish

    Sry I frget to mention I m frm general categ,,.

  13. rohit

    Q.3) Advanced sunrise and delayed sun- set found in the sky are due to the phenomenon of

    It is due to total internal reflection LUCENT GK pg no: 450 point no 5.

      1. Prateek

        Yes,it’s due to atmospheric refraction!

    1. Nishant kumar

      It is due to refraction of light…. clearly mentioned in 12th NCERT of optics section….

    2. yatin

      leave what ncert and lucent says, try to make a ray diagram for this phenomenon, than you will understand that its refraction.

    3. Vaibhav

      Sunrise and delayed sunset is due to looming and looming is a part of TIR.

  14. mhon

    Question no.1 regarding IT related.I have doubt regarding the CRT,PLASMA,LED as we are using the new TV technology which uses PLASMA these days replacing LED..

  15. shaoyifu

    The transformer is also used to convert dc to ac along with an inverter correct me if I am wrong……

      1. shaoyifu

        Well i donot remember any source for this but i am an electronics engineer and In power conversion applications an inverter is an electronic transformer which converts power from a Direct Current (D.C.) source into Alternating Current (A.C.) power. Power conversion inverters can be divided into two sub-categories, voltage-fed inverters and current-fed inverters. Voltage-fed inverters are more common than the current-fed inverters. The electronic transformers used in inverter circuits are often called inverter transformers. Inverters produce A.C. power by switching the polarity of the D.C. power source across the D.C. power source’s load. . However give me some time I’ll try to find out some source and post.

        1. Kartikeya

          Brother.. Transformer is used there to either step-up voltage (and hence step-down current) or step-down it (step-up-ing the current) before feeding it to the inverter. Polarity switching was done solely by the inverter itself..

        2. raghuBeer

          Inverter is not a transformer. The question is not about an inverter either. There is a fundamental difference between an inverter and a transformer. Inverter converts ac to dc. Whereas a transformer changes the voltage and current levels only.

        3. vaibhav

          as far as my knowledge of power electronics goes, chopper is used for dc to ac conversion in the inverter. Transformers’ only purpose is to step up and step down the voltage.

    1. H.s

      i am an electrical engineer and as far as i know the only function of transformer is to step up or step down the voltage supply.since it is made up of coils and works on the principle of magnetic induction it can not convert d.c into a.c.

      1. shaoyifu

        The question is not dat what can a transformer do. It says what is it used for

    2. AKG47

      There is no transformer on EARTH which can convert DC to AC….

  16. Gunjan

    what could be the probable cut offs (General candidates) for this year’s CAPF?
    Last year it was 97 marks for general category.

  17. sahil

    Natural gas quest.
    Why not ans opt c.
    Becoz quest ask gases and contains “mainly” ….
    And methane is 80% other gas are already included in quest itself…???

  18. sourabh

    electricity meter includes a microcomputer bt itself is a analog computer.
    correct me if i m wrong..??

    1. AKG47

      NO microcomputer, it’s microprocessor programming on chip….. analog is answer

  19. shahid

    good endeavor by mrunal bai

  20. prakash

    when is upsc going to publish its key for capf 2013? is there any other source for getting answer key..pls do send me the link if there is as such

  21. mayur ghungrud

    aprx.i will get 130 marks i paper 1 of capf is there i qualify for phase 2

  22. H.s

    Analog Computer works on continuous range of
    varied values of Physical quantities like
    Temperature, Speed, Voltage, Pressure etc. and
    generates approximate results.
    The Digital computer is designed with digital
    circuits in which there are two levels (logic 0 and
    logic 1) for an input and output signal. This
    computer is very much useful to solve complex
    problems in Engineering and Technology and
    hence it has increasing use in the field of design,
    research and data processing. If this digital
    computer is used for any type of application, then
    it is called as General Purpose Computer and
    Special Purpose Computer when it is used for
    specific application/program.
    electric meter comes under the analog computer as quantity measured is continous in the form of analog signals.

  23. Chandan Kumar

    Natural Gas question.
    Since the question explicitly mentions ‘mixture’, the option C is certainly untrue.
    The option D can also be rejected considering that even if you remove CO and H2, the gas will still be called a Natural Gas. They are present in NG (in small quantity sometimes and in other times absent) but not an essential component of the mixture called Natural Gas.
    The option A is accurate description of that mixture.

  24. Rakesh Kuldeep

    CAPF 2013 Result when will declare…

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