SPI Practice Test Questions And Answers!

Sound waves are longitudinal mechanical waves. Longitudinal waves are characterized by the motion of particles in the same direction as the wave propagation. In the case of sound waves, the particles of the medium (such as air, water, or solids) vibrate back and forth in the same direction as the wave travels. This vibration creates compressions and rarefactions, resulting in the transmission of sound energy. Therefore, sound waves are classified as longitudinal mechanical waves.

wavelength is the length of space that one wave occupies, usually measured in mm, meters, inches.

Intensity is a crucial acoustic variable that quantifies the energy carried by a sound wave per unit area. It is an essential factor in determining the perceived loudness of a sound, as a higher-intensity sound wave produces a louder sound. The unit of measurement for sound intensity is watts per square meter (W/m²). The intensity of a sound wave decreases with increasing distance from the source due to the spreading of the wave in space. This phenomenon is known as the inverse square law, which states that the intensity of a sound wave is inversely proportional to the square of the distance from the source.

The propagation speed of a wave is equal to the frequency of the wave multiplied by its wavelength. This relationship is defined by the wave equation, where the speed of a wave is determined by the frequency at which it oscillates and the distance it travels per cycle (wavelength). Therefore, the correct answer is frequency.

This statement is not true because waves with identical frequencies can interfere constructively or destructively depending on their phase. If the waves are in-phase, they will interfere constructively, but if they are out-of-phase, they will interfere destructively.

Soft tissue has certain properties that affect the propagation of ultrasound waves. These properties are referred to as acoustic propagation properties. This includes the ability of soft tissue to transmit, absorb, and scatter ultrasound waves. Understanding these properties is important in medical imaging as it helps in interpreting ultrasound images and diagnosing various conditions.

The frequency closest to the lower limit of ultrasound is 20,000 Hz (or 20 kHz). Ultrasound refers to sound waves with frequencies higher than the upper limit of human hearing, which is approximately 20,000 Hz. The lower limit of ultrasound is typically considered to be around 20 kHz, while the upper limit can extend to several gigahertz (GHz) for some applications. Ultrasound waves with frequencies close to the lower limit, such as 20 kHz, are often used in various applications, including medical imaging, sonar, and non-destructive testing. At these frequencies, ultrasound can effectively propagate through various mediums, such as water, tissue, and metals, and provide valuable information for diagnosis, detection, or material characterization.

Ultrasonic waves refer to sound waves that have a frequency above the range of human hearing, which typically starts at around 20 kHz. Therefore, the sound wave with a frequency of 30 kHz is considered ultrasonic. Diagnostic imaging, such as ultrasound imaging, utilizes sound waves in the megahertz range (MHz), typically between 2-18 MHz, to create detailed images of internal body structures. Since 30 kHz is below this range, it is least useful in diagnostic imaging.

The speed of ultrasound in soft tissue is closest to 1,540 m/s (or 1.54 km/s). Ultrasound waves are high-frequency sound waves that have a higher frequency than the audible range for humans. In soft tissues, such as muscle, fat, and blood, the speed of ultrasound is relatively constant and is typically between 1,540 m/s and 1,580 m/s. This property allows ultrasound waves to be used in medical imaging, such as sonography, where the reflections of ultrasound waves are used to produce images of internal organs and tissues. Ultrasound is also used in other applications, such as non-destructive testing and underwater sonar, due to its ability to propagate through various mediums and provide detailed information about the materials it interacts with.

The frequency of a wave is the number of complete cycles of the wave that occur in one second. In this case, the wave has a period of 1 millisecond, which means it completes one cycle in 1 millisecond. To find the frequency, we can use the formula: frequency = 1 / period. Therefore, the frequency of the wave with a 1 msec period is 1 kHz (1 kilohertz), which means it completes 1,000 cycles in one second.

When the compressibility and density of a material decrease, the propagation speed increases. This is because when a material is less compressible, it is able to transmit waves more efficiently, resulting in a faster propagation speed. Similarly, when the density of a material decreases, there are fewer particles to interact with, allowing the waves to travel faster. Therefore, decreasing compressibility and density both contribute to an increase in propagation speed.

Range resolution is determined by the source and the medium. Range resolution refers to the ability of a system to distinguish between two closely spaced targets in the range direction. The source characteristics, such as the wavelength of the signal, and the properties of the medium through which the signal propagates, such as the speed of propagation, affect the range resolution. By controlling these factors, the source and the medium can influence the ability of the system to resolve targets at different ranges.