Chapter 4:Particle nature of matter

gravitational force

The force of attraction between any two bodies is directly proportional to the product of their masses and is inversely proportional to the square of the distance between them.

brownian movement

the random motion of small particles suspended in a gas or liquid

stationary states

The electron does not radiate electromagnetic energy in these special orbits, and because the energy is constant
with time these are called stationary states.

atomic nucleus

The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom.

proton

a stable particle with positive charge equal to the negative charge of an electron

alpha particle

a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes

cathode ray

a beam of electrons emitted by the cathode of an electrical discharge tube

diffraction

when light passes sharp edges or goes through narrow slits the rays are deflected and produce fringes of light and dark bands

spectral lines

distinct lines emitted by photoelectric effect

quantization

the act of dividing into quanta or expressing in terms of quantum theory