ABO (American Board of Opticianry) Practice Test

The correct answer is "Corpuscular." This refers to the theory that light consists of tiny particles, called corpuscles, that travel in a straight line and can also exhibit wave-like properties. This theory, also known as the particle theory of light, was proposed by Sir Isaac Newton and later disproved by Thomas Young's double-slit experiment, which demonstrated the wave-like nature of light. Option A, "Photons," is incorrect as this term is used to describe particles of light according to the modern theory of quantum mechanics. Option C, "Apex," is incorrect and unrelated to light. Option D, "Refraction," is also incorrect as it refers to the bending of light as it passes through different mediums.