Lec 6 Problems Solution -1

This lecture, part of a physics course, focuses on solving numerical problems related to quantum mechanics and radiation. The instructor begins by calculating the energy of a photon from a green laser with a wavelength of 532 nm, using the formula E = hc/λ and converting to electron volts. Next, he determines the maximum wavelength of light that can excite an electron across a semiconductor band gap of 1.2 eV. The third problem applies Wien’s displacement law to find the peak wavelength of radiation from a pan at 360°C, yielding about 5057 nm in the infrared. The fourth problem uses Planck’s radiation law to calculate the power emitted per unit area at the Sun’s peak wavelength of 500 nm, resulting in a value of approximately 4.75×10^12 W/m². Finally, the instructor calculates the number of photons in a 1-meter-long beam from a 1 mW He-Ne laser (wavelength 633 nm), finding about 1.06×10^7 photons. He then discusses the concept of single-photon experiments and the double-slit experiment, emphasizing how the interference pattern builds up from individual photon detections, illustrating the wave-particle duality.