When a light wave encounters an object, it is transmitted, reflected, absorbed, refracted, polarized, diffracted, or scattered depending on the composition of the object and the wavelength of the light. Waves interact with matter in different ways that we'll discuss in this lesson. Interactions can occur when waves pass from one medium to another, bounce back like an echo, bend or extend around or across edges, or come into direct contact with each other. These ways in which waves can interact with matter are called reflection, refraction, diffraction, and interference.
Each type of interaction is described in detail below. The quantum energy of microwave photons is in the range of 0.00001 to 0.001 eV, which is in the range of energies that separate the quantum states of molecular rotation and torsion. Infrared radiation penetrates the skin more than visible light and can therefore be used to obtain photographic images of subcutaneous blood vessels. Health problems related to exposure to UV rays mainly relate to the 290 to 330 nm wavelength range, the range called UVB.
The interaction of microwaves with matter other than metallic conductors will consist of spinning molecules and producing heat as a result of that molecular movement. When waves hit an obstacle head-on, the reflected waves bounce back in a straight line in the direction where they came from. This high frequency means that the noise does not bother the patient and high amplitudes can be used, but ultrasound is mainly chosen because high-frequency sounds have a small wavelength. Light from a light source, such as the sun or a light bulb, illuminates the object and some of the light is reflected.
Ships in the ocean use the reflective properties of sound waves to determine the depth of the ocean. Different parts of the electromagnetic spectrum have very different effects on interaction with matter.
