The vast surface area of the ocean covers about three quarters of the planet’s surface. The majority of energy we receive from the sun is accordingly absorbed by the ocean. The optical properties of the water body play a critical role in understanding the processes involved, and interpreting the measurement results from various active and passive sensors. For example, reflectance from the ocean’s surface and bottom of the shallow seas not only affects the signals returned, but also carries information about their properties, which are integral parts of the ocean sensing and monitoring process. The amount of light being scattered along its transmission path is a function of the water itself, modulated by the temperature, salinity, and density of the environments, as well as the constituents within. It is assumed that readers are familiar with basic optical definitions, from which we introduce concepts often used in the field of ocean optics. This chapter serves as the foundation of following chapters, and readers are encouraged to read through it, unless you are confident with the terminology and symbols used in ocean sensing literature. These basic terms are touched on briefly during discussions of light attenuation, light propagation, and light generation topics.
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