Electromagnetic waves can travel through a vacuum because they do not require a medium to propagate. These waves are self-propagating, consisting of oscillating electric and magnetic fields that support and perpetuate each other's existence. This characteristic allows electromagnetic waves to move through the vacuum of space, where there is no matter. On the other hand, sound waves are mechanical waves that rely on the vibration of particles in a medium (like air, water, or solid materials) to transfer energy from one place to another. In a vacuum, where there are no particles to vibrate, sound waves cannot propagate. This fundamental difference underlines the unique nature of electromagnetic waves and their ability to transmit energy across the vast emptiness of space.

The ability of electromagnetic waves to penetrate materials varies significantly across different wavelengths. Generally, longer wavelengths like radio and microwaves can penetrate through materials better than shorter wavelengths like X-rays and gamma rays. For instance, radio waves can travel through walls, which is why we can receive radio signals inside buildings. Microwaves, with slightly shorter wavelengths, can penetrate clouds and are used in satellite communication. In contrast, ultraviolet rays, X-rays, and gamma rays have much shorter wavelengths and higher energies, which allow them to pass through or be absorbed by different materials. X-rays, for example, can penetrate soft tissue but are absorbed by denser materials like bone, enabling their use in medical imaging. The interaction of electromagnetic waves with materials depends on factors such as the energy of the waves, the density of the material, and the material's atomic structure, influencing their penetration ability.

Electromagnetic waves can indeed be polarized. Polarization refers to the orientation of the wave's electric field. In unpolarized light, such as sunlight, the electric field oscillates in multiple directions perpendicular to the direction of wave propagation. When light is polarized, the electric field oscillates predominantly in one direction. Polarization can be achieved through various methods, such as reflection, refraction, or by passing light through a polarizing filter. Polarized electromagnetic waves have several practical applications. For example, polarized sunglasses reduce glare by blocking horizontally polarized light reflected off surfaces like water or roads. In telecommunications, polarization is used to reduce interference between signals. In photography, polarizing filters enhance contrast and saturation. Polarization is also crucial in scientific studies, such as in the analysis of crystal structures and in the study of electromagnetic radiation from astronomical sources.

Infrared waves are used in thermal imaging due to their ability to be emitted by all objects that have a temperature above absolute zero. Unlike visible light, which depends on an object's ability to reflect light, infrared radiation is emitted by objects based on their thermal energy. This characteristic makes infrared waves ideal for thermal imaging, which visualizes the temperature distribution of an object or scene. Infrared cameras detect the infrared radiation emitted by objects and convert it into an image that depicts temperature variations. Warmer objects emit more infrared radiation than cooler ones, allowing the camera to create a thermal image. This technology is widely used in various fields, including security, medicine (to detect inflammation or poor blood flow), building inspections (to identify heat leaks), and night vision equipment.

The frequency of electromagnetic waves is directly proportional to their energy. This means that waves with higher frequencies have higher energies. The energy of an electromagnetic wave is determined by the equation E = hf, where E is energy, h is Planck's constant, and f is the frequency of the wave. Therefore, electromagnetic waves like gamma rays and X-rays, which have very high frequencies, also possess high energies. This high energy allows gamma rays to be used in cancer treatment, as they can penetrate tissues and damage cancer cells. On the other hand, lower frequency waves like radio waves have much less energy, making them safe for communication purposes. The relationship between frequency and energy is fundamental in understanding the behaviour and application of electromagnetic waves across different regions of the spectrum.