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प्रश्न
How are mechanical waves different from electromagnetic waves?
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उत्तर
| Electromagnetic waves | Mechanical waves |
| They can travel in vacuum. | They cannot travel in vaccum. They need a material medium for their propagation. |
| These are formed by the periodic vibrations of mutually perpendicular electric and | These are formed by the vibrations of the medium particles about their mean positions. These vibrations can be along the direction of propagation of wave or perpendicular to it. |
| These are traverse in nature. | These waves can be transverse as well as longitudinal. |
संबंधित प्रश्न
Define amplitude term in relation to a wave.
A wave passes from one medium to another medium. Mention one property of the wave out of speed, frequency or wavelength which changes.
Name two sound absorbing materials (or objects) which can make our big room less echoey.
What do you understand by the ‘Echolocation system of Dolphins’?
(i) A man stands at a distance of 68 m from a cliff and fires a gun. After what time interval will he hear the echo, if the speed of sound in air is 340 ms−1?
(ii) If the man had been standing at a distance of 12 m from the cliff would he have heard a clear echo?
What is mean by the reflection of sound?
Explain Reflection at curved surfaces.
Match the following:
| 1. | Stethoscope | a. | Repeated reflections |
| 2. | Echogram | b. | Multiple reflections |
| 3. | SONAR | c. | Ultrasonic waves |
| 4. | Reverberation | d. | Speed of underwater objects |
