Briefly describe the three kinds of defense in our immune system

The immune system includes three lines of defense against foreign invaders: physical and chemical barriers, nonspecific resistance, and specific resistance. The first line of defense are the physical and chemical barriers, which are considered functions of innate immunity.

the diagram which shows forces as either balanced = same speed or unbalanced = accelerarting

waves moving from a fast medium to a slow medium will experience a reflection as light travels more slowly than red light. total internal reflection occurs when the critical angle is.