Final answer:
Blind spots behind a truck can span 20-30 feet and are not visible due to mirror angles and vehicle size. Objects in convex mirrors can appear farther away than they actually are. Clear mountain streams seem shallower than they are due to the refraction of light.
Step-by-step explanation:
Blind spots are areas you cannot see in a mirror and can be 20-30 feet behind a truck. This is due to the angles at which the mirrors are set and the physical size of the truck obstructing the view. Similarly, when we consider the statement "objects in some mirrors are closer than they appear," it relates to the convex mirrors used on vehicles. Convex mirrors provide a wider field of view, which causes objects to look smaller and further away than they really are, hence the warning for drivers since it affects the perception of distance.
Reflecting on the phenomenon where clear mountain streams are always a little bit deeper than they appear, this is due to the refraction of light. Light bends, or refracts, as it moves from air into water, which makes objects under the water appear closer to the surface than they truly are. This is an essential concept of physics known as Essential Knowledge 6.E.2, dealing with the refractive properties of light when moving between mediums of different densities.