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 2002Science and Technology · Physics: Optics and Sound
Q1. 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?
Explanation
Statement 1 is incorrect: According to Rayleigh scattering, light with shorter wavelengths (e.g., blue light) is scattered more than light with longer wavelengths (e.g., red light).
Statement 2 is incorrect: The refractive index of water is approximately 1.33, so the speed of light in water is about 1/1.33 0.75° the speed in a vacuum.
Statement 3 is correct: Radio waves are a type of electromagnetic radiation generated when electrical charges oscillate in an antenna. These oscillations create alternating electric and magnetic fields that propagate as waves. This principle is the basis of wireless communication technologies like radio, TV, and mobile networks.
Statement 4 is correct: The Doppler effect is used in radar guns to measure the speed of moving vehicles by analyzing the frequency shift of reflected radio waves.
UPSC 2002Science and Technology · Physics: Optics and Sound
Q2. 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 phenomena is a mirage formed?
Explanation
A mirage is primarily caused by terrestrial heating and the refraction of light. Mirage causes deceptive appearance of a distant object or objects caused by light ray bending (refraction) in different density layers of air. Terrestrial Heating: The ground is intensely heated by the sun (such as a hot road or desert). This heats the air near the surface, making it less dense than the cooler air above. The temperature gradient creates a gradient in the refractive index of the air. Refraction of Light: Light from the sky or distant objects passes through the layers of air with varying temperatures and densities. The light bends (refracts) as it moves from cooler, denser air to hotter, less dense air. This bending creates the illusion of water or a mirrored surface on the ground.
Answer key for these questions
Q
UPSC year
Correct answer
1
2002
(d) 3 and 4
2
2002
(c) 1 and 3
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.
