Who explained the photoelectric effect?

The photoelectric effect and photon theory are among the most important discoveries in modern physics. Option A is wrong. Newton proposed the corpuscular theory of light in 1704 treating light as tiny particles. He did not explain the photoelectric effect. Newton's theory was largely superseded by wave theory and then quantum theory. Option B is wrong. Huygens proposed the wave theory of light in 1678. He explained reflection and refraction using wave fronts. He had no knowledge of the photoelectric effect which was discovered much later. Option C is wrong. Maxwell developed the electromagnetic wave theory of light in 1865 showing light is an EM wave. While this was a great achievement Maxwell's theory is a classical wave theory and could not explain the quantum photoelectric effect. Option D is CORRECT. The image states: प्रकाश का फोटोन सिद्धांन किसके द्वारा प्रतिपादित किया गया — आइन्स्टीन द्वारा. Albert Einstein explained the photoelectric effect in 1905 (his miracle year) by proposing that light consists of discrete energy packets called photons. He received the Nobel Prize in Physics in 1921 specifically for this explanation. The photoelectric effect was discovered by Heinrich Hertz in 1887 but Einstein provided the theoretical explanation using Planck's quantum concept.