## Nature

Nature is the natural, physical and living world.

• Nature in the broadest sense, is all of planet Earth, our solar system and the universe beyond.
• In a more limited sense whilst everything around us is evidence of nature, from the global phenomena of oceans, continents and climate, nature is a carpet of interconnected life forms composed of individual plants, insects and animals.
• Although humans are part of nature, human activity and the human world with its cities, agriculture and industries are sometimes understood as a separate category from other natural phenomena.
• The study of nature is a large part of the histories of science and art.

https://en.wikipedia.org/wiki/Nature

## Normal

If one line is normal to another, then it is at right angles. So in geometry, the normal is a line drawn perpendicular to and intersecting another line.

In optics, the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.

• Light travels in a straight line through a vacuum or a transparent medium such as air, glass, or still water.
• If light encounters a force, an obstacle or interacts with an object, a variety of optical phenomena may take place including absorption, dispersion, diffraction, polarization, reflection, refraction, scattering or transmission.
• Optics treats light as a collection of rays that travel in straight lines and calculates the way in which they change direction (deviate) when encountering different optical phenomena.
• When the normal is drawn on a ray diagram, it provides a reference against which the amount of deviation of the ray can be shown.
• The normal is always drawn at right angles to a ray of incident light at the point where it arrives at the boundary with a transparent medium.

https://en.wikipedia.org/wiki/Geometrical_optics

## Normal

If one line is normal to another, then it is at right angles. So in geometry, the normal is a line drawn perpendicular to and intersecting another line.

In optics, the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.

• Light travels in a straight line through a vacuum or a transparent medium such as air, glass, or still water.
• If light encounters a force, an obstacle or interacts with an object, a variety of optical phenomena may take place including absorption, dispersion, diffraction, polarization, reflection, refraction, scattering or transmission.
• Optics treats light as a collection of rays that travel in straight lines and calculates the way in which they change direction (deviate) when encountering different optical phenomena.
• When the normal is drawn on a ray diagram, it provides a reference against which the amount of deviation of the ray can be shown.
• The normal is always drawn at right angles to a ray of incident light at the point where it arrives at the boundary with a transparent medium.

https://en.wikipedia.org/wiki/Geometrical_optics