Which of the following concepts introduced by Einstein laid the foundation for modern quantum mechanics?

آئن اسٹائن کے ذریعہ متعارف کروائے جانے والے مندرجہ ذیل میں سے کون سے تصورات نے جدید کوانٹم میکانکس کی بنیاد رکھی؟

Photoelectric effect

Principle of Relativity

Theory of General Relativity

None of these

Explanation

Einstein's explanation of the photoelectric effect (1905) introduced the concept of quantized energy (photons), laying the foundation for quantum mechanics.

This discovery led to Einstein receiving the Nobel Prize in Physics (1921) and helped develop wave-particle duality in quantum theory.