Give an example of a wave that does not need a medium in which to travel and a wave that does need a medium.

An electromagnetic wave plays a pivotal role in the way we receive and transmit information through space. Unlike mechanical waves, these waves do not require a medium to propagate. This means they can travel through the void of space as well as through air or other materials. Electromagnetic waves consist of oscillating electric and magnetic fields at right angles to each other and the direction of the wave's propagation. A key characteristic of these waves is their speed in a vacuum, which is approximately 299,792 kilometers per second (the speed of light).

Electromagnetic waves encompass a broad spectrum that includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. All these waves have different wavelengths and frequencies, which define their unique properties and applications, such as using radio waves for communication or X-rays for medical imaging.

Mechanical waves are disturbances that travel through a medium due to the interaction of particles within that medium. Unlike electromagnetic waves, mechanical waves require a material substance, like air, water, or solid objects, to move through. There are different types of mechanical waves, including

transverse waves

where the displacement of the medium is perpendicular to the direction of wave propagation, and

longitudinal waves

where the displacement is parallel to the direction of wave propagation.

Sound waves are a prime example of longitudinal mechanical waves, as they involve sequential compressions and rarefactions of particles within the medium that carry the wave's energy from one location to another. The requirements of a medium for mechanical wave propagation mean that these waves cannot travel through a vacuum, as there are no particles to facilitate the movement.

Wave propagation refers to the way waves travel through a medium or even without one, in the case of electromagnetic waves. The propagation of waves involves the transfer of energy from one point to another, with the characteristics of the medium, or its absence, affecting the speed and form of the wave. Music from a speaker illustrates how sound waves propagate through air particles, moving in a concentric pattern away from the source.

The rate at which waves propagate can vary dramatically. For example, sound waves travel at about 343 meters per second in air at room temperature, much slower compared to the speed of light. Moreover, factors such as temperature, density, and elasticity of the medium can significantly influence the speed and direction of mechanical wave propagation. In contrast, electromagnetic waves always move at the speed of light in a vacuum, regardless of these factors.

Light waves are a specific type of electromagnetic wave that is visible to the human eye. These waves lie within a small range of the electromagnetic spectrum, nestled between infrared and ultraviolet light. Their wavelengths range roughly from 380 to 750 nanometers. Apart from allowing us to perceive colors and see our surroundings, light waves have critical applications in technology such as optical fibers used for telecommunication and lasers for surgeries.

Light behaves uniquely because it exhibits dual nature: it can act like a wave and like particles known as photons. This duality explains phenomena like diffraction and interference as well as the photoelectric effect. Light waves can travel through various media including air, water, and glass, but their speed reduces compared to their velocity in a vacuum, a phenomenon that explains refraction when light passes through different materials.

Sound waves represent an important category of mechanical waves. They correspond to the pressure variations produced by the vibration of an object, such as a guitar string or vocal cords, which then propagate through a medium. These longitudinal waves consist of compressions and rarefactions that move sequentially through the substance, such as air, water, or solids.

The speed of sound is not constant and is affected by the medium's properties; it travels faster in solids compared to liquids and gases due to the tighter bonding of particles. Temperature also plays a role; sound travels faster in warmer conditions as molecules move more rapidly. Humanity relies heavily on sound waves, not just for communication through speech and music but also for applications like sonar used in navigation and echocardiograms in medical diagnostics.