Correct Response: C. In the late 19th century, classical physics predicted that at short wavelengths, a black body in thermal equilibrium would emit an infinite amount of energy, a situation sometimes referred to as the ultraviolet catastrophe. Planck's analysis of the spectrum emitted by a blackbody showed that the situation could be resolved by postulating that light is quantized. Einstein applied this postulate to explain the photoelectric effect, setting the stage for further acceptance of the idea of quantization. Michelson's and Morley's effort (A) to detect the luminiferous ether influenced the development of the theory of relativity. Röntgen's discovery of the emission of X-rays from a vacuum tube (B) represented the discovery of a new type of radiation in the form of electromagnetic waves. This was very significant, but it did not directly lead to the quantum theory of light. Hertz's detection of electromagnetic radiation (D) demonstrated the existence of electromagnetic waves, lending support to Maxwell's electrodynamic theory. This led to the understanding of light as a wave, but not as a photon, which is the electromagnetic particle associated with the quantum theory of light.
