Which of the following statements about electromagnetic waves, sound waves and water waves is/are correct?
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A person rings a metallic bell near a strong concrete wall. He hears the echo after 0.3 s. If the sound moves with a speed of 340 m/s, how far is the wall from him?
A sound wave has frequency of 2 kHz and wavelength of 35 cm. If an observer is 1.4 km away from the source, after what time interval could the observer hear the sound?
Ultrasonic waves of frequency 3 × 105 Hz are passed through a medium where speed of sound is 10 times that in air (Speed of sound in air is 300 m/s). The wavelength of this wave in that medium will be of the order of
The speed of a body that has Mach number more than 1 is
Which one of the following waves does not belong to the category of the other three?
Bats detect obstacles in their path by receiving the reflected
Which one of the following waves is used for detecting forgery in currency notes?
An object is vibrating at 50 hertz. What is its time period?