Particle & Ray Model of Light

  • Idea that light has particle-like properties

  • Photons are particles of light (Carries more energy as the frequency increases and wavelength decreases)

  • Photoelectric effect: when light shines on metal surface, surface can (not always) give off electrons

  • Red light shines on metal surface (Electrons never given off no matter how bright/how long red light shines on metal)

  1. Has lower frequency & longer wavelength

  2. Photons of red light don’t carry enough energy to make metal give off electrons

  • Blue light shines on metal surface(Electrons always given off, no matter how dim/briefly blue light shines on metal)

  1. Has higher frequency & shorter wavelength

  2. Photons of blue light carries enough energy to make metal give off electrons

  • If light was a wave

  • Any wavelengths of light (Ex. red) could pile up enough energy when it hits metal to cause electrons to be given off by metal

  • Wave model of light couldn’t explain photoelectric effect

Ray Model of Light:

  • Idea that light travels in straight lines

  • Ray is arrow used to show direction of straight-line path of light

  • Diagrams that involve rays called ray diagrams

  • Used to visualize, study, & predict how light behaves