Lenses and mirrors: optics in everyday life

In short: Lenses and mirrors direct light. Converging lenses focus rays and produce images, diverging lenses spread them. Glasses, cameras and magnifying glasses use these principles.

In more detail: Light is refracted on passing between materials and reflected at smooth surfaces (licht-und-farben).

In detail

• Reflection: Angle of incidence equals angle of reflection; mirrors produce a virtual image.
• Refraction: Light changes direction, for example on entering water or glass.
• Converging lens (convex): Focuses light at the focal point; magnifying glass, camera lens, telescope.
• Diverging lens (concave): Helps with short-sightedness.
• Focal length: Distance from lens to focal point (brennweite-und-bildwinkel).
• Eye: Cornea and lens create an image on the retina (sinnesorgane-auge-ohr-nase).
• Rainbow: Refraction and reflection in water droplets (regenbogen-entstehung).
• Optical fibre: Total internal reflection guides light through thin fibres.