The length of a lens is the distance from the center of the lens to
its principal focus.

Focal length

Explanation:

The Focal length of a lens is the distance from the center of the lens to

its principal focus.

1) when you rub your hands together quickly, the kinetic energy is converted to mechanical energy.2) thermal energy from the sun travels to earth as infrared waves.3) energy is transferred through the matter of space by electromagnetic waves. 4) when a match is burned, chemical potential energy is converted to thermal and radiant energy. 5) seismicwaves are caused by back and forth movement , or vibration, of an object. 6) mechanicalenergy in an engine changes thermal energy into kinetic energy to make a car move.

Fitness is the ability to perform only very light levels of physical activity.