…the scientific study of sight and the behaviour of light, or the properties of transmission and deflection of other forms of radiation…
…the use of thin flexible fibres of glass or other transparent solids to transmit light signals, chiefly for telecommunications or for internal inspection of the body…
…the branch of physics that deals with the behaviour of electrons and electron beams in magnetic and electric fields…
…the branch of science that deals with the effect of electric fields on light and on the optical properties of substances…
