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 2000Science and Technology · Physics: Optics and Sound
Q1. A noise level of 100 decibel would correspond to:
Explanation
Decibels (dB) are units used to measure the intensity of sound. The decibel scale is logarithmic, meaning each 10 dB increase represents a tenfold increase in sound intensity.
Option (d) is correct: A noise level of 100 decibels corresponds to Noise from a machine shop. A sound at 100 decibels is quite loud. It is typical of sounds like those found in a machine shop or at a loud concert. For reference: 0 decibels is the threshold of hearing (just audible sound). 30-40 decibels corresponds to a quiet room. 60-70 decibels corresponds to ordinary conversation. 100 decibels is in the range of very loud noise, such as machinery or a chainsaw. Directions: The following items consist of two statements, one labeled as the Assertion (A) and the other as Reason (R). You have to answer these items using the code given below. (2000)
UPSC 2000Science and Technology · Physics: Optics and Sound
Q2. When a CD (compact disc used in audio and video systems) is seen in sunlight, rainbow-like colours are seen. This can be explained on the basis of the phenomenon of:
Explanation
In the case of a compact disc (CD), when sunlight or any other light source hits its surface, the following optical phenomena occur. Diffraction: The CD’s surface contains tiny, closely spaced grooves that act like a diffraction grating. This causes the light to spread out into different colors, creating the rainbow effect that is visible. Refraction: Light also passes through the transparent plastic layer of the CD, and as it enters and exits this layer, it bends due to the change in the refractive index between the plastic and air. Transmission: Some light also passes through the CD material, further contributing to the observed effects. Together, these phenomena--refraction, diffraction, and transmission--combine to produce the beautiful rainbow-like colors seen when a CD is viewed in sunlight.
Answer key for these questions
Q
UPSC year
Correct answer
1
2000
(d) Noise from a machine shop
2
2000
(d) refraction, diffraction and transmission
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.
