The unit deals with radiation in the environment. The first three chapters are focused on
light, a visible form of radiation. The chapters touch on the properties of light through a
variety of contexts. In Light and Sight, you will learn about reflection and refraction and how
light enables us to see the things in our environment. Light also enables us to "capture
moments" through photographs. Light from distant objects can also be captured as
described in the section on optical instruments. The last two chapters are about a form of
radiation that cannot be detected by our senses. This form of radiation we call nuclear
radiation is very much a part of living on earth. Natural background radiation and the
various applications of ionizing radiation provide the contexts for learning about this topic.
Understanding concepts in nuclear radiation is essential for you to weigh the risks and
benefits associated with the applications of radioactivity in medicine, power generation
industry, or for basic scientific research.