The wave-particle dual nature of light was discovered from experimental observations and from theoretical works of Max Planck and Albert Einstein during the beginning of the twentieth century. This paper reveals that wave-particle duality is just one aspect of the all dual nature of light (electromagnetic waves) and electromagnetic fields and that light and electromagnetic fields manifest dual natures in other ways also. For example, light is not only a local phenomenon as conventionally viewed, but also a non-local phenomenon. Light behaves both according to ether theory and emission theory. The speed of light is both constant (c) and variable ( c ± V). The phase velocity of light is independent of source and observer velocity and is always constant c, while the group velocity of light varies with observer velocity but is independent of source velocity. Light acts as if it travels both in a straight line and in curved path, at the same time! Electrostatic lines of force behave as if they are both straight and curved lines. Electrostatic fields behave as if they ‘propagate’ both at the speed of light and with infinite speed, at the same time! This paper is a summary of the findings reported in previous papers published by this author. An extensive theoretical research carried out by this author in an attempt to explain the Michelson-Morley experiment, the Sagnac effect and other light speed experiments led to uncovering of the broader and more fundamental nature of duality in electromagnetism.