sound wave

1.Which of the following uses ultrasound?

• Echo Cardiography
• SONAR
• Sonography
• All of these

2. What should be the minimum distance between the source and reflector in water so that echo is her distinctly ? (speed of sound in water 1400 m/s)

• 70 m
• 17 m
• 17 - 18
• None of these

3. By increasing length of the pendulum it's frequency is:

• Decreases
• Increases
• Doesn't change
• None of thess

4. Human ear can hear sound wave of 20 Hz. It's wavelength will be: ( speed of sound 330 m/s)

• 20 m
• 16.5 m
• 16.5 mm
• Data is insufficient

5. Oscillating pendulum in air performs:

• Free vibration
• Damped vibration
• Resonance vibration
• All of the above