Practice MCQ Questions and answers on Physics-GK

The speed of sound is faster in solid materials and slower in liquids or gases. The velocity of a sound wave is affected by two properties of matter: the elastic properties and density.

An echo is a sound that is repeated because the sound waves are reflected back.

Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. During propagation, waves can be reflected, refracted, or attenuated by the medium. Now if we consider these cases, then the train which is arriving towards us having whistles of higher pitch because it propagates through a medium which is coming towards us but the train which is leaving propagating through a medium moving further away from the listener and thus produced whistle of lower pitch.

The sound waves produced by the bats are ultrasonic waves. Bats emit sounds at typically 2 or 3 times higher pitch than we can hear. Sounds above human hearing are usually called ultrasonic.

During rainy days, the moisture content is more in the atmosphere and speed or velocity of sound increases with increase in humidity. Hence the sound travels faster on rainy days.

Reflection is responsible for the echo of sound wave.

The loudness of sound is directly proportional to the amplitude of the wave. The loudness of the sound increases with increase in the amplitude vibration. The unit of loudness is decibel.

Bat can hear ultrasonic sound.

Sonar is the instrument which uses sound waves to measure the depth of oceans.

Megahertz is a measurement of frequency.