Question 1: Define ultrasound and explain how it differs from audible sound.

Answer: Ultrasound refers to sound waves with a frequency above 20 kHz, which is higher than the upper limit of human hearing, typically used in medical and industrial applications.

Question 2: Describe the basic mechanism by which ultrasound is used in consumer products such as distance sensors or cleaning devices.

Answer: Ultrasound waves are emitted by a transducer, reflect off objects or surfaces, and are received back by the transducer. The time taken for the echoes to return is used to calculate distances or clean surfaces.

Question 1: An ultrasound sensor in a car parking system emits waves at a frequency of 40 kHz. If the speed of ultrasound in air is approximately 343 m/s, calculate the wavelength of the ultrasound wave.

Answer: wavelength = speed / frequency = 343 m/s ÷ 40,000 Hz = 0.00858 m or 8.58 mm

Question 2: If an ultrasonic cleaning device operates at a frequency of 2 MHz and the wavelength in water is approximately 1.5 mm, verify the speed of ultrasound in water used in this device.

Answer: speed = wavelength × frequency = 1.5 × 10^-3 m × 2,000,000 Hz = 3000 m/s

Question 1: Describe a basic experimental setup to test the effectiveness of an ultrasonic cleaning device. Include the variables that need to be controlled.

Answer: An ultrasonic cleaning tank with a transducer attached to generate ultrasound waves. Variables to control include water temperature, ultrasound frequency and power, and the type and amount of dirt or debris on objects. Safety precautions involve avoiding direct exposure to high-intensity ultrasound and ensuring proper handling of electrical equipment.

Question 1: A consumer ultrasonic distance sensor measures a reflection time of 0.00005 seconds for an object. Using the speed of ultrasound in air (343 m/s), calculate the distance to the object. Explain the steps involved.

Answer: Distance = (speed × time) / 2 = (343 m/s × 0.00005 s) / 2 = 0.00858 m or 8.58 mm. The division by 2 accounts for the round trip of the ultrasound wave.

Question 1: Identify two consumer products that utilise ultrasound technology and briefly explain how ultrasound enhances their function.

Answer: Ultrasound in car parking sensors helps detect objects and measure distance accurately. Ultrasonic cleaners use high-frequency sound waves to remove dirt from delicate objects effectively.

Question 2: Discuss safety considerations that should be taken into account when using ultrasound devices in consumer products.

Answer: Ultrasound devices should operate within safe frequency and power levels to prevent tissue damage or hearing damage. Proper shielding and user instructions are important to minimise exposure. Devices should comply with safety standards and include warnings if necessary.