Wave and photon models of lightEdexcel International A Level Physics: Mind map

Exam questions on Wave and photon models of light

1. A teacher is comparing the wave model and the photon model of light. She demonstrates Young's double-slit experiment with a laser and then discusses how light is emitted and absorbed by atoms.
   Explain why a particle model of light cannot account for the fringes observed in the double-slit experiment.2 marks
2. A laser pointer emits red light of wavelength 650 nm. A second laser pointer emits green light of wavelength 532 nm with the same power output. Use the Planck constant h = 6.63 × 10⁻³⁴ J s and the speed of light c = 3.00 × 10⁸ m s⁻¹.
   Calculate the energy of one photon from the red laser pointer.2 marks
3. A sodium street lamp emits yellow light of wavelength 589 nm. The power emitted by the lamp as light is 20 W. Use the Planck constant h = 6.63 × 10⁻³⁴ J s and the speed of light c = 3.00 × 10⁸ m s⁻¹.
   Calculate the energy of one photon emitted by the lamp.3 marks