# Features of All Waves

• All waves transfer energy and information without transferring matter.
• Waves are categorised as either transverse or longitudinal, based on their direction of vibration compared to the direction of energy transfer.
• Transverse waves include light and all electromagnetic waves, ripples on water, and waves on a string. They vibrate perpendicular to the direction of energy transfer.
• Longitudinal waves include sound waves and ultrasound waves. They vibrate parallel to the direction of energy transfer.
• A wave cycle involves a complete vibration consisting of one peak and one trough in transverse waves, or one compression and one rarefaction in longitudinal waves.

# Wave Behaviour

• Waves can undergo several behaviours including reflection, refraction, diffraction and interference.
• Reflection involves the bouncing back of waves when they hit a reflective surface, leading to an echo or the formation of an image in a mirror.
• Refraction is the change of direction and speed of a wave when it enters a different medium, leading to bending of waves.
• Diffraction is the spreading out of waves when they pass through a gap or around obstacles. This behaviour is more prominent when the gap is comparable to the wavelength of the waves.
• Interference refers to the interaction of two waves meeting, resulting in constructive (increasing amplitude) or destructive (decreasing amplitude) interference.

# Wave Measurements

• The wavelength is the distance from a point on one wave to the identical point on the next wave, for example, from one peak to the next peak.
• The frequency of a wave is the number of waves produced or passing a point in one second, and it’s measured in Hertz (Hz).
• The amplitude is the maximum displacement of a point on the wave from its undisturbed position, in other words, the height from the middle line to the peak in a transverse wave or compression in a longitudinal wave.
• The speed of the waves can be calculated using the equation: wave speed = frequency x wavelength.

# Properties and Use of Waves

• Several fields like medicine, engineering and communications use waves to observe structures and phenomena that are otherwise impossible.
• Ultrasound waves are used for medical imaging and treatment as they can pass through body tissues and reflect back at boundaries to create images.
• Seismic waves encountered in the study of earthquakes provide vital information about the structure of the Earth’s interior.
• Electromagnetic waves, including light, enable us to create images of galaxies billions of light years away, as well as of minuscule structures within cells.

# Practicals with Waves

• The behaviour and properties of waves can be explored with practical experiments like the ripple tank for water waves.
• Investigations of reflection and refraction can be done with light-box experiments.
• Sound wave experiments can involve exploration of pitch and volume with musical instruments.
• Through these experiments, one can prove the relationships and behaviours of waves, and validate the wave equation, v = f λ.