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GS Paper IUPSC Prelims 2002
Health & Medicine
Question No. 260Interactive Test Mode
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Q260. Consider the following statements: 1. Light of longer wavelengths is scattered much more than the light of shorter wavelength. 2. The speed of visible light in water is 0.95 times the speed in vacuum. 3. Radio waves are produced by rapidly oscillating electrical currents. 4. To detect the overspeeding vehicles, police use the Doppler effect of reflected short radio waves. Which of these statements are correct?

Consider the following statements:

  1. Light of longer wavelengths is scattered much more than the light of shorter wavelength.
  2. The speed of visible light in water is 0.95 times the speed in vacuum.
  3. Radio waves are produced by rapidly oscillating electrical currents.
  4. To detect the overspeeding vehicles, police use the Doppler effect of reflected short radio waves.

Which of these statements are correct?

Select the correct option below (or cross out options to eliminate)
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Official Answer Key & Detailed Solution

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Official UPSC Answer KeyUPSC Prelims 2002 • Science and Technology

Correct Answer: Option (D) — 3 and 4

Concept & Option Breakdown

Standard Reference Verified

Statement 1 is incorrect: By Rayleigh scattering, scattering intensity is inversely proportional to the fourth power of wavelength (I ∝ 1/λ^4); shorter wavelengths (blue/violet) scatter much more than longer wavelengths (red). Statement 2 is incorrect: The refractive index of water is n ≈ 1.33. Speed in water = c / 1.33 ≈ 0.75 c, not 0.95 c. Statement 3 is correct: Oscillating electric charges in an antenna create varying electric and magnetic fields, generating radio waves. Statement 4 is correct: Police radar speed guns emit short radio waves/microwaves and measure the Doppler frequency shift of the reflected wave to calculate vehicle speed.

Elimination Heuristic & Exam Approach

Rayleigh's law (I ∝ 1/λ⁴) immediately invalidates statement 1. Eliminate (a) and (b). Knowing refractive index of water is 4/3 (~1.33) eliminates statement 2.

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Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 2002 (Q260)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Health & Medicine
Official Answer KeyOption (D) — 3 and 4

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Frequently Asked Questions — UPSC Prelims 2002 Q260

What is the official answer for UPSC Prelims 2002 GS Paper I Question 260 (Science and Technology)?

The official UPSC answer key for this 2002 Science and Technology (Health & Medicine) question is Option (D): "3 and 4". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 2002 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Health & Medicine". You can explore all repeated questions from Health & Medicine 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 Health & Medicine UPSC Prelims question using option elimination?

Rayleigh's law (I ∝ 1/λ⁴) immediately invalidates statement 1. Eliminate (a) and (b). Knowing refractive index of water is 4/3 (~1.33) eliminates statement 2.

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