Light as a Wave
Light travels as an electromagnetic wave — oscillating electric and magnetic fields. Light of different wavelengths appears as different colors. Red light has long wavelengths (~700nm), violet has short (~400nm). White light contains all colors mixed together.
Reflection
When light hits a smooth surface, it bounces off at the same angle it arrived. That's why mirrors work. The law: angle of incidence = angle of reflection. Rough surfaces scatter light in many directions — that's diffuse reflection.
Refraction
Light bends when it moves from one medium to another (like air to water). This is why a straw looks bent in a glass of water. Different colors bend by different amounts — that's how prisms create rainbows.
The Eye as an Optical Instrument
Your eye is a remarkable optical system: cornea and lens focus light onto the retina. Problems like nearsightedness (focus too strong) and farsightedness (focus too weak) are fixed by corrective lenses that adjust the focusing power.