Energy and Earth - Fundamentals of the Physical Environment - page 26

the wavelength (λ, Greek lambda). It is an important
indicator of the properties of the electromagnetic radiation.
Figure 2.3 The electromagnetic spectrum. µm stands for
micrometre, one millionth of a metre.
distance from the sun to Earth of about 150 million km, it takes this energy about 8·3
minutes to reach us.
When solar radiation is absorbed, it is converted from radiant to other forms of energy.
Much is altered to thermal (heat) energy . In reality, it warms Earth's surface and the
atmosphere by exciting the molecules of which they are composed. In simple terms, the
radiant energy (which involves disturbance of magnetic and electric fields) is transmitted
into the molecules making up the ground and atmosphere, with a resulting change in the
type of energy.
Thermal energy can therefore be considered as energy involved in the motion of
extremely small components of matter. The energy of motion is referred to as kinetic
energy (and thus thermal energy is sometimes described as the kinetic energy of
molecules). Any moving object possesses kinetic energy, and it is through the use of this
energy that, for example, a stone thrown into a lake can disturb the water and produce
waves. It is also through the exploitation of kinetic energy that turbines and engines are
able to produce heat, light and so on.
Chemical energy represents a form of electrical energy bound up within the chemical
structure of any substance. It is released in the form of thermal or kinetic energy when the