MCQ
Ultrasound is of frequency:
- ABelow $20\ Hz$
- BAbove $20\ Hz$
- CBelow $20\ kHz$
- ✓Above $20\ kHz$
Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range. Ultrasound is thus not separated from normal (audible) sound by differences in physical properties, only by the fact that humans cannot hear it. Although this limit varies from person to person, it is approximately $20,000$ hertz in healthy, young adults. Ultrasound devices operate with frequencies from $20\ kHz$ up to several gigahertz.
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| Object | Density (kg/m$^3$) | Volume (m$^3$) | Mass (kg) |
| $A$ | - | $2$ | $4000$ |
| $B$ | $8000$ | $4$ | - |
| $C$ | $2000$ | - | $1000$ |
| $D$ | - | $4$ | $2000$ |
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S.No.
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Specific Characteristic
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Physical state
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$1.$
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Ionised gases
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$2.$
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Most ordered state
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$3.$
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Least ordered state
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$4.$
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Fixed volume, no shape
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$5.$
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Cooling gas at super low temperature
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