The atoms are usually neutral state. The agitation of a gas increases when it absorbs heat. If enough heat is absorbed, electrons are stripped from atoms and matter is ionized, saying that it is in plasma state.

When a wave which propagates in different planes passes through a polarising filter, we say that it has become polarised.

The positon vector tells us where the moving body is at every instant. The trajectory marks the line the body has moved along

Properties which can be measured and expressed with a number and a unit, magnitudes. Length, mass, volume, the quantity of a substance, voltage, etc, are magnitudes.

Light behaves in two ways: like a particle and like a wave. The way a photoelectric cell works shows the corpuscular behaviour of light.

Phosphorescence is the luminescence produced by a mineral during a more or less long period of time, after the source of exciting radiation has ceased.

Oil is the product of the decomposition of the remains of microscopic living organisms which millions of years ago inhabited the seas, lakes and river estuaries. Oil today has a multitude of applications. This is why is it essential not to waste it simply as fuel. The following visual shows how it is formed and how it is used.

The educational resource shows an interactive animation about the perpetual motion: If such a system were possible, it would be a type of perpetual motion.

Relation between the magnitude frequency and the magnitude period

The ancient Greeks knew that the parabolic mirrors are paraboloids of revolution which have the property of concentrating the rays at the focus of the paraboloid.

Concept of Ohm's law. The following visual is useful for studying Ohm's Law.

Concept of Ohm's law

Observation concept

Concept of nuclear fusión

Nuclear energy is the energy stored in the nuclei of atoms and it is released in the nuclear reactions of fission and fusion.

Concept of nuclear stability

Concept of nuclear fission

The educational resource shows information about a nuclear power station, how it works and its advantages and its disadvantages.

This visual is to explain how images are formed in the mirrors.

Formation of nitid specular images