Physics: Optics and Sound: UPSC Previous Year Questions (Science and Technology)
2 previous year UPSC Prelims questions on Physics: Optics and Sound (Science and Technology). Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 1–2 of 2 questions
UPSC 2003Science and Technology · Physics: Optics and Sound
Q1. Diffusion of light in the atmosphere takes place due to:
Explanation
The diffusion of light in the atmosphere occurs mainly due to dust particles and aerosols, which scatter sunlight in all directions. This scattering, known as Mie scattering, happens when particles like dust or water droplets are comparable in size to the wavelength of light, scattering all wavelengths almost equally. It causes the sky to appear uniformly bright and ensures visibility even in shadows. Other aerosols like Water Vapors, Smoke, etc can also contribute to the diffusion effect. However, dust particles are the most prominent cause in this context.
UPSC 2003Science and Technology · Physics: Optics and Sound
Q2. Which one of the following statements is not correct?
Explanation
Option (c) is incorrect: Humidity (water vapor) actually increases the speed of sound in air. This is because water molecules are lighter than nitrogen and oxygen molecules, reducing the overall density of the air. The speed of sound in humid air is higher than in dry air at the same temperature. Options (a), (b) and (d) are correct:
The velocity of sound in air increases with temperature because higher temperatures increase the energy of air molecules, allowing sound to travel faster. The velocity of sound in air is independent of pressure at constant temperature since both pressure and density change proportionally, leaving the speed unchanged. The velocity of sound is unaffected by amplitude and frequency as it depends only on the medium>s properties like temperature, density, and composition.
Answer key for these questions
Q
UPSC year
Correct answer
1
2003
(b) dust particles
2
2003
(c) The velocity of sound in air decreases as the humidity increases.
Frequently asked questions
How many previous year UPSC questions are there on Physics: Optics and Sound?
This page covers 2 previous year UPSC Prelims GS Paper-I questions on Physics: Optics and Sound (Science and Technology), asked from 1996 to 2009. Each has the correct answer and an explanation.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Physics: Optics and Sound?
Questions on Physics: Optics and Sound (Science and Technology) are available for 8 years, from 1996 to 2009. Use the Year filter to practise a single paper.
