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Ultrasonic waves of frequency 3 × 10<sup>5</sup> 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

Correct Answer: 1 cm

Simplify the value of $$\frac{{{\text{0}}{\text{.9}} \times {\text{0}}{\text{.9}} \times {\text{0}}{\text{.9 + 0}}{\text{.2}} \times {\text{0}}{\text{.2}} \times {\text{0}}{\text{.2 + 0}}{\text{.3}} \times {\text{0}}{\text{.3}} \times {\text{0}}{\text{.3}} - {\text{3}} \times 0.9 \times {\text{0}}{\text{.2}} \times {\text{0}}{\text{.3}}}}{{{\text{0}}{\text{.9}} \times {\text{0}}{\text{.9 + 0}}{\text{.2}} \times {\text{0}}{\text{.2 + 0}}{\text{.3}} \times {\text{0}}{\text{.3}} - 0.9 \times {\text{0}}{\text{.2}} - {\text{0}}{\text{.2}} \times {\text{0}}{\text{.3}} - 0.3 \times 0.9}} = ?$$

$$\frac{{38 \times 38 \times 38 + 34 \times 34 \times 34 + 28 \times 28 \times 28 - 38 \times 34 \times 84}}{{38 \times 38 + 34 \times 34 + 28 \times 28 - 38 \times 34 - 34 \times 28 - 38 \times 28}}$$            is equal to = ?

A sound wave with frequency f travels through air at speed v. With what speed will a sound wave with frequency 4f travel through the air?

The figure given below shows the function of ultrasonic waves. What are these techniques called?
Sounds waves and Motion mcq question image

Consider the following statements.
1. Light of longer wavelength is scattered much more than the light of shorter wavelength.
2. The speed of visible light in water is 0.95 times the speed in vacuum.
3. Radio waves are produced by rapidly oscillating electrical currents.
4. To detect the overspeeding vehicles, police use the Doppler effect of reflected short radio waves.
Which of these statements are correct?

A source of sound frequency 600Hz is placed inside water. The speed of sound in water is 1500 m/s and in air it is 300 m/s. The frequency of sound is recorded by an observer, who is standing in the air is?

Sound waves travel at 350 m/s through warm air and at 3,500 m/s through brass. What happens to the wavelength of a 700 Hz acoustic wave as it enters brass from warm air?

What is the frequency range of the ultrasonic sound waves used by the ultrasonic sensors?

Consider the following statements.
1. In sound waves, the vibrations are perpendicular to the direction in which the wave travels.
2. Sound waves are elastic waves.
Which of the statement(s) given above is/are correct?

$$\eqalign{ & {\text{The}}\,{\text{value}}\,{\text{of}} \cr & \frac{{0.1 \times 0.1 \times 0.1 + 0.02 \times 0.02 \times 0.02}}{{0.2 \times 0.2 \times 0.2 + 0.04 \times 0.04 \times 0.04}}\,\text{is}: \cr} $$