Reality can be difficult to define as our senses can be deceived and devices can transform real inputs into illusions. The document discusses how electromagnetic radiation spans from radio waves to gamma rays and our senses of vision, hearing, touch, taste and smell help construct our perception of reality. However, devices like X-ray machines take real X-ray inputs and produce virtual bone images, transforming real inputs into illusory outputs. This challenges the distinction between what is real versus virtual.