How do electromagnetic waves interact with matter?

Electromagnetic waves interact with matter by being absorbed, reflected, transmitted, or causing ionisation.

When electromagnetic waves encounter matter, several things can happen depending on the type of wave and the material it meets. Firstly, the waves can be **absorbed** by the material. This means the energy from the wave is taken in by the atoms or molecules of the substance, often causing them to vibrate more and increase in temperature. For example, when sunlight (which is made up of various electromagnetic waves) hits your skin, it warms you up because your skin absorbs the energy.

Secondly, electromagnetic waves can be **reflected**. This occurs when the waves bounce off the surface of a material. A common example is visible light reflecting off a mirror. The smooth surface of the mirror causes the light waves to bounce back in a specific direction, allowing you to see your reflection.

Thirdly, electromagnetic waves can be **transmitted** through a material. This means the waves pass through the substance without being absorbed or reflected. For instance, visible light passes through clear glass, allowing you to see through windows. Different materials transmit different types of electromagnetic waves to varying extents. For example, X-rays can pass through soft tissues in your body but are absorbed by denser materials like bones, which is why they are used in medical imaging.

Lastly, some electromagnetic waves, particularly those with higher energy like ultraviolet (UV) rays, X-rays, and gamma rays, can cause **ionisation**. This means they have enough energy to knock electrons out of atoms, creating ions. This process can be harmful to living tissues, which is why excessive exposure to these types of radiation can be dangerous and is carefully controlled in medical and industrial settings.

Understanding these interactions helps us use electromagnetic waves in various technologies, from medical imaging to communication systems, and even in everyday items like microwaves and remote controls.