Applications of Waves

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Medical Applications of Waves

Seeing inside the body

Reflection Refraction Light

Medical imaging has transformed healthcare. Doctors can now see inside the human body without surgery, diagnose conditions earlier and monitor treatments more effectively. Three major wave-based technologies are X-rays, ultrasound and MRI.

X-rays

X-rays are high-energy electromagnetic waves that pass through soft tissue but are absorbed by denser materials like bone. When X-rays pass through the body and hit a detector on the other side, they create a shadow image. Bones appear white because they absorb the X-rays; soft tissues appear darker because the X-rays pass through.

X-rays are fast and relatively inexpensive, making them ideal for checking broken bones and dental problems. However, because X-rays are ionising radiation, exposure must be limited. Lead aprons and shields protect parts of the body that do not need imaging.

Ultrasound

Ultrasound uses high-frequency sound waves (mechanical waves, not electromagnetic) to create images. A transducer sends sound waves into the body and detects the echoes that bounce back from different tissues. A computer uses these echoes to build a real-time image.

Ultrasound is safe for pregnant women because it does not use ionising radiation. It is commonly used to monitor fetal development, examine the heart and detect problems with organs. However, ultrasound cannot penetrate bone effectively, so it is not used for imaging the brain or lungs.

MRI (Magnetic Resonance Imaging)

MRI uses strong magnetic fields and radio waves to create highly detailed images of soft tissues, including the brain, spinal cord and joints. The patient lies inside a large magnet. The magnetic field causes atoms in the body to align, and radio waves disturb this alignment. When the atoms return to their original state, they emit signals that are detected and turned into images.

MRI does not use ionising radiation, making it safer than X-rays and CT scans for repeated imaging. However, it is expensive, takes longer and cannot be used on patients with certain metal implants. At Stage 5, you do not need to understand the detailed physics of MRI — what matters is that it uses magnetic fields and radio waves, not X-rays.

Modern communication relies heavily on electromagnetic waves. Three key technologies are radio and microwave broadcasting, optical fibre and satellite communication.

Radio and microwaves

Radio waves carry AM and FM radio broadcasts, television signals and mobile phone data. Microwaves, which have slightly higher frequencies, are used for mobile phone networks, Wi-Fi and satellite communication. Because microwaves can be focused into narrow beams, they are ideal for sending large amounts of data over long distances.

Mobile phone towers transmit and receive microwave signals to connect calls and data. In rural Australia, where laying cables is expensive, microwave links and satellite communication are especially important for connecting remote communities.

Optical fibre

Optical fibres are thin strands of glass that carry data as pulses of light. Light enters one end of the fibre and reflects off the inner walls as it travels, staying inside the fibre even when it bends. This is called total internal reflection. A single optical fibre can carry millions of phone calls or internet connections at once.

Optical fibre is the backbone of the National Broadband Network (NBN) in Australia. It provides much faster internet speeds than traditional copper wires because light has a much higher frequency than electrical signals, allowing more data to be transmitted.

Remote sensing uses satellites and aircraft to detect electromagnetic radiation from Earth's surface. Different materials reflect and emit different wavelengths, so sensors can identify vegetation, water, minerals and temperature patterns from space.

In Australia, remote sensing is used to monitor bushfires, floods and drought. Satellites detect infrared radiation (heat) from fires, allowing emergency services to track fire spread in real time. They also measure microwave radiation to estimate soil moisture, helping farmers manage crops during dry periods.

Radio astronomy detects radio waves from space. Because radio waves pass through dust and gas that block visible light, radio telescopes can see objects that optical telescopes cannot. Australia's Parkes Observatory (Murriyang) and the future Square Kilometre Array (SKA) in Western Australia are world-leading radio astronomy facilities. In 2020, the Parkes telescope helped receive the first high-definition video from the Moon in over 40 years.

Aboriginal and Torres Strait Islander Peoples have deep, sophisticated knowledge of wave phenomena developed over tens of thousands of years. This knowledge is practical, empirical and closely tied to survival and culture.

Sound and vibration: Many Aboriginal cultures use sound for communication over long distances. The didgeridoo produces low-frequency sound waves that travel far across flat terrain. Traditional knowledge also includes interpreting vibrations in the ground — reading seismic signals from distant events to understand what is happening in the landscape.

Light and astronomical observation: Aboriginal astronomy is among the oldest in the world. Indigenous observers track the movement of stars (light waves from distant suns) to create calendars, predict seasons and navigate across the continent. The Emu in the Sky, a dark constellation recognised by many Aboriginal groups, demonstrates deep understanding of how light and dark regions in the Milky Way can be interpreted.

Water waves and coastal knowledge: Aboriginal coastal peoples have intimate knowledge of ocean swells, tides and currents — all wave phenomena. This knowledge was used for fishing, travel and predicting weather. Before European arrival, Aboriginal people navigated between islands and across open water using wave patterns, star positions and seasonal wind patterns.