Acme Ai
A
अ
GS Paper IUPSC Prelims 2013
Biotechnology & Genetics
Question No. 115Interactive Test Mode
00:00
+2-0.66

Q115. Consider the following statements: 1. Size of the sun at dusk 2. Colour of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions?

Consider the following statements:

  1. Size of the sun at dusk
  2. Colour of the sun at dawn
  3. Moon being visible at dawn
  4. Twinkle of stars in the sky
  5. Polestar being visible in the sky Which of the above are optical illusions?
Select the correct option below (or cross out options to eliminate)
PrevNext Question

Official Answer Key & Detailed Solution

3D PYQ Realm

Ready to check the official UPSC Answer Key?

Click any option above to test yourself under exam conditions, or reveal the explanation directly.

Official UPSC Answer KeyUPSC Prelims 2013 • Science and Technology

Correct Answer: Option (C) — 1, 2 and 4

Concept & Option Breakdown

Standard Reference Verified

Statements 1, 2, and 4 are optical illusions:

  1. The Sun appears larger near the horizon at dusk due to the Ponzo illusion / atmospheric horizon illusion.
  2. The reddish colour of the Sun at dawn/dusk is due to Rayleigh scattering of light by atmospheric particles.
  3. The twinkling of stars is an optical effect caused by atmospheric refraction through layers of varying air density and refractive index.

Statements 3 and 5 are not optical illusions: 3. The Moon being visible at dawn is a regular astronomical phenomenon depending on its lunar phase. 5. The Polestar's visibility is due to its geometric alignment above Earth's rotational axis, not an illusion.

Elimination Heuristic & Exam Approach

Statements 3 and 5 are simple celestial positions determined by orbital geometry, not deceptive optical tricks or atmospheric illusions. Eliminating 3 and 5 leaves only (c).

Reviewed by Avinash Sir & Acme AI Research Team

Practice Full-Length & Sectional Prelims Mocks on this Interface

50 simulated tests in the APT Prelims Test Series (₹1,493) or 1-on-1 Mentorship with Avinash Sir.

1-on-1 MentorshipOpen Test Platform

Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 2013 (Q115)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Biotechnology & Genetics
Official Answer KeyOption (C) — 1, 2 and 4

Related & Repeated Prelims PYQs (4)

Questions from other UPSC Prelims years testing the same or closely linked concept.

View Cluster in 3D Graph
2002 • Q26184% Match

Consider the following natural phenomena: 1. Terrestrial heating 2. Reflection of light 3. Refraction of light 4. Diffraction of light Due to which of these ph

Science and Technology • Health & MedicineSolve
1996 • Q29683% Match

Consider the following statements: A person in a spaceship located half way between the earth and the sun will notice that the: (1) The sky is jet black. (2) st

Science and Technology • Space & ISROSolve
1999 • Q26981% Match

Consider the following statements: 1. If a person looks at a coin which is in a bucket of water, the coin will appear to be closer than it really is. 2. If a pe

Science and Technology • Health & MedicineSolve
2013 • Q19181% Match

Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1. Dispersion 2. Refraction 3. Int

Science and Technology • Health & MedicineSolve

More PYQs from Science and Technology (Biotechnology & Genetics)

Master the Science and Technology syllabus cluster by practicing these related previous year questions.

View All Science and Technology PYQs
2024 • Q1Biotechnology & Genetics

"Membrane Bioreactors" are often discussed in the context of:

Science and TechnologyPractice
2024 • Q2Biotechnology & Genetics

Which one of the following is synthesised in the human body that dilates blood vessels and increases blood flow?

Science and TechnologyPractice
2024 • Q62Health & Medicine

Consider the following activities: 1. Identification of narcotics on passengers at airports or in aircraft 2. Monitoring of precipitation 3. Tracking

Science and TechnologyPractice
2024 • Q63Health & Medicine

Which one of the following words/phrases is most appropriately used to denote “an interoperable network of 3D virtual worlds that can be accessed simu

Science and TechnologyPractice
2024 • Q93Nanotechnology

In which of the following are hydrogels used? 1. Controlled drug delivery in patients 2. Mobile air-conditioning systems 3. Preparation of industrial

Science and TechnologyPractice
2024 • Q99Space & ISRO

Consider the following statements: Statement-I: Giant stars live much longer than dwarf stars. Statement-II: Compared to dwarf stars, giant stars have

Science and TechnologyPractice
2024 • Q134Defence Technology

Consider the following aircraft: 1. Rafael 2. MiG-29 3. Tejas MK-1 How many of the above are considered fifth-generation fighter aircraft?

Science and TechnologyPractice
2024 • Q142Nuclear Energy

With reference to radioisotope thermoelectric generators (RTGs), consider the following statements: 1. RTGs are miniature fission reactors. 2. RTGs ar

Science and TechnologyPractice

Frequently Asked Questions — UPSC Prelims 2013 Q115

What is the official answer for UPSC Prelims 2013 GS Paper I Question 115 (Science and Technology)?

The official UPSC answer key for this 2013 Science and Technology (Biotechnology & Genetics) question is Option (C): "1, 2 and 4". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 2013 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Biotechnology & Genetics". You can explore all repeated questions from Biotechnology & Genetics in Acme AI's 3D Prelims PYQ Realm or practice 50 full-length and sectional tests in the APT Prelims Test Series.

How can I solve this Biotechnology & Genetics UPSC Prelims question using option elimination?

Statements 3 and 5 are simple celestial positions determined by orbital geometry, not deceptive optical tricks or atmospheric illusions. Eliminating 3 and 5 leaves only (c).

Beyond Previous Year Questions

Structured Prelims Practice & Mentorship

Pair previous year question analysis with full-length simulated mock tests and 1-on-1 faculty guidance.

APT 2027 • 50 Prelims Tests17% OFF

Acme Prelims Test Series (APT)

Built to eliminate 1/3rd negative marking losses and 50–50 option traps through structured simulation and NCERT-backed keys.

  • 50 High-Yield Tests: Subject Sectionals, Current Affairs, CSAT Paper II & Full-Length Simulators
  • 1/3rd Penalty & Trap Analytics: Identify whether marks are lost to over-attempting or conceptual gaps
  • Option-by-Option NCERT Keys: Detailed distractor analysis and elimination logic for every question
  • Custom PDF-to-Mock Generator: Convert your revision notes or current affairs PDFs into practice tests
Complete 50-Test Package
₹1,493₹1,799• Valid till Prelims 2027
Explore APT Test SeriesTry Free Mock
1-on-1 Personal MentorshipCapped at 10 Seats

1-on-1 UPSC Mentorship with Avinash Sir

Weekly 1-on-1 strategy reviews, daily study accountability, and personalized MCQ attempt audits with an experienced UPSC mentor.

  • Weekly 1-on-1 Sessions: Direct mentorship with Avinash Sir (Former Plutus IAS Mentor, UPSC & UPPCS Mains Written)
  • APT 50-Test Series Included: Full Prelims GS1 & CSAT test series bundled at no additional cost
  • Mock Attempt & Elimination Audit: Question-by-question review to calibrate your risk and attempt accuracy
  • Prelims & Integrated Tracks: Available as dedicated Prelims mentorship or end-to-end Prelims + Mains guidance
Prelims & Integrated Tracks
17% OFF• Includes APT 50-Test Series
Explore 1-on-1 MentorshipCompare Tracks
Previous QuestionWhich one of the following is likely to be the most inflationary in its effect?
Next QuestionQuit India Movement was launched in response to: