Q1. The bats can fly in the dark because
(a) They have a better vision in the dark
(b) The light startles them
(c) They produce ultrasonics
(d) None of the above
Answer: (c) They produce ultrasonics
Explanation: Bats use echolocation, emitting ultrasonic sound waves that bounce off objects and return to them. This allows them to navigate and hunt in complete darkness by interpreting the echo patterns, not relying on vision.
Q2. Different notes are produced by a flute by
(a) Closing and opening the holes
(b) Closing the holes
(c) Closing the alternate holes
(d) Closing the last two holes
Answer: (a) Closing and opening the holes
Explanation: A flute produces different musical notes by altering the length of the vibrating air column. This is done by closing and opening holes along its body, which changes the pitch and frequency of the sound.
Q3. In microphone, transformation of energy takes place from
(a) Sound into electrical energy
(b) Electrical into sound energy
(c) Sound into mechanical energy
(d) Mechanical into sound energy
(UPSC Prelims 1980)
Answer: (a) Sound into electrical energy
Explanation: A microphone converts sound waves into electrical signals, enabling amplification, recording, or transmission of audio.
Q4. “Mach Number” is a term associated with the speed of
(a) Ships
(b) Cars
(c) Aeroplanes
(d) Light
(UPSC Prelims 1983)
Answer: (c) Aeroplanes
Explanation: The Mach Number measures the speed of an object relative to the speed of sound. It is commonly used in aeronautics to describe supersonic aircraft performance, where Mach 1 equals the speed of sound.
Q5. Microphone is a device in which the
(a) Sound waves are converted into electrical energy and then reconverted into sound after transmission
(b) Sound waves are directly transmitted
(c) Electrical energy is converted into sound waves directly
(d) Amplification is not required at all
(UPSC Prelims 1985)
Answer: (a) Sound waves are converted into electrical energy and then reconverted into sound after transmission
Explanation: A microphone converts sound waves into electrical signals, which can be amplified, recorded, or transmitted. These signals are later reconverted into sound, making it essential for audio communication systems.