Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Waves and optics → Sound waves ↓


Ultrasound and its uses


Sound waves are fascinating phenomena that are not only the medium for our favorite catchy tunes but also serve a more serious purpose in modern technologies. A special type of sound wave, known as ultrasound, plays a vital role in a variety of fields. This lesson explores ultrasound, its creation, properties, and its fascinating range of uses in industries and medicine. By the end, you'll have a comprehensive understanding of this extraordinary technology.

Understanding sound waves

Before diving into ultrasound, it's important to understand what a sound wave is. Sound waves are disturbances that travel through a medium such as air, water or solids. These waves move by causing particles to vibrate and transfer energy. Sound waves are characterized by three main properties: wavelength, frequency and amplitude.

  • Wavelength: It is the distance between successive points of the same phase in the wave, such as peak to peak or trough to trough.
  • Frequency: The number of waves that pass a point in one second, measured in hertz (Hz).
  • Amplitude: The height of the wave, which determines the loudness of the sound.

What is ultrasound?

Ultrasound refers to sound waves with a frequency higher than the upper audible limit of human hearing. Humans can usually hear sounds with frequencies between 20 Hz and 20,000 Hz. Ultrasound waves have a frequency higher than 20,000 Hz (20 kHz).

Although we cannot hear these sounds, they can be detected and used by special equipment. Ultrasound technology takes advantage of the high frequency and short wavelength of these waves, allowing them to carry more energy and penetrate various materials very efficiently.

Properties of ultrasound

Ultrasound waves have unique properties that make them useful for a variety of applications:

  • High frequency and short wavelength: These properties enable ultra-precise measurements. They can resolve minute details, which is important for detailed imaging.
  • Directional propagation: Ultrasound can be directed into narrow beams and can propagate easily through mediums without scattering much.
  • Reflection and refraction: Ultrasound has the ability to reflect from surfaces and to bend when passing through mediums with different densities.

Uses of ultrasound

Due to the unique properties of ultrasound it has wide applications in both medical and industrial fields.

Medical uses

Ultrasound is an important tool in the medical field. It is non-invasive, safe, and provides real-time results. Some of the primary medical uses of ultrasound include:

  • Diagnostic imaging: This is the most commonly recognized use of ultrasound, especially in prenatal scanning. Doctors use ultrasound machines to create images of the fetus during pregnancy. This helps assess the growth and development of the unborn baby. Here is a basic diagram of how it works: 
                    +---+ +----------------+ |US | --> | | | P | | BODY | +---+ <-- | | +----------------+ (US P = Ultrasound Probe)
  • Cardiology: Ultrasound, known as echocardiography, is used to examine the condition of the heart. It can determine the size, structure, and movement of the heart's parts.
  • Biopsy guidance: Ultrasound helps surgeons guide needles to take tissue samples (biopsies), reducing the risk of damage to surrounding structures.
  • Treatment applications: High-intensity ultrasound can be used in physical therapy to stimulate tissue repair and to reduce pain or relax muscles.

Industrial uses

Ultrasound is also used in industry, particularly in quality control and non-destructive testing:

  • Non-destructive testing (NDT): In manufacturing, ultrasound can be used to examine materials and structures without causing damage. For example, it can detect cracks, voids or inclusions in metals or composite materials. Here's how ultrasound waves reflect off defects: 
                    +------------------+ | Material | | | | X XX X | +------------------+ Legend: X = Defect
  • Sonar: In navigation and mapping, sound is used to identify the distance and direction of underwater objects in sound navigation and ranging.
  • Ultrasonic cleaning: High-frequency ultrasound can clean delicate instruments. It generates cavitation bubbles, which remove dirt from the surfaces of objects immersed in liquid.
  • Food processing: Ultrasound helps improve the texture and shelf-life of food products or speed up extraction processes such as juice extraction.

How ultrasound works: general principles

Ultrasound systems generally work based on the resonance principle. A transducer made of piezoelectric materials generates ultrasound by converting electrical pulses into sound waves. These waves penetrate the object and reflect back to the sensor when they strike various media or surfaces.

The basic components of an ultrasound system include:

  • Transducer: It sends and receives sound waves.
  • Display unit: Converts the received signal into an image or data that can be analyzed.
  • Control panel: Allows the operator to adjust settings for optimal imaging.

The time it takes for the ultrasound echo to return provides information about the distance travelled by the sound and, thus, the position of the object that reflected the wave. The intensity of the echo gives information about the characteristics of the object.

Ultrasound imaging: a closer look

There are several processes for creating an image using ultrasound:

  1. The ultrasound probe emits sound waves into the body.
  2. Sound waves travel through the body and collide with boundaries between tissues (e.g., fluid and soft tissue, soft tissue and bone).
  3. Some sound waves reflect back to the probe, while other waves travel further and reach the other boundary and are reflected back.
  4. The reflected waves are picked up by the probe, transmitted to the machine, which calculates the distance from the probe to the tissue or organ boundaries using the speed of sound in tissue (about 1,540 m/s) and the time it takes for each echo to return.
  5. This machine creates a two-dimensional image by displaying the distance and intensity of the echo on the screen.

Mathematics of sound waves

The study of sound waves involves some mathematical calculations. Consider the basic wave equation:

        v = f * λ

Where:

  • v is the speed of the wave
  • f is the frequency
  • λ (lambda) is the wavelength

With ultrasound, these principles remain, but we work with much higher frequencies, making more detailed resolution possible.

Factors affecting ultrasound image quality

Several factors can affect the quality of an ultrasound image:

  • Frequency used: Higher frequencies provide better resolution but have lower penetration depth.
  • Transducer properties: This includes the design and size of the array elements.
  • Tissue characteristics: Different tissues have different acoustic properties, which can affect wave propagation.
  • Operator skill: The quality of imaging depends largely on how well the technician manages the device.

Advantages and limitations of ultrasound

Benefits

  1. Safe and non-invasive.
  2. No ionizing radiation.
  3. Real time imaging capability.
  4. Widely available and portable.

Boundaries

  1. In some dense materials the penetration depth is limited.
  2. Image quality largely depends on operator skill.
  3. Sometimes the images may be less detailed than other imaging methods such as CT or MRI.

Interesting facts

  • Dolphins and bats use a sonar-like system called echolocation to navigate and hunt. They emit ultrasonic pulses that reflect off objects, helping them figure out where an object is.
  • Some of the smallest medical ultrasound transducers for high-resolution arterial imaging are inserted into blood vessels via catheters.

Conclusion

Ultrasound technology is a remarkable application of sound waves that deeply impacts many aspects of modern life. From prenatal scans to industrial defect detection, the mechanisms behind ultrasonic technologies provide us with great information and tools for scientific and practical purposes. As technology develops, its range of applications continues to evolve, establishing ultrasound as an important technological frontier.


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Ultrasound and its uses

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