Note 1 Light

The Electromagnetic Spectrum

• Starts with a vibration in the magnetic field which vibrates the electric field. The transverse waves move out perpendicular to each other.

• All waves move at the speed of light (3.00×10^8 m/s in a vaccuum)

• Waves have 3 properties:

  • Wavelength: The distance between successive peaks of a wave, which determines the color of visible light.

  • Frequency: The number of waves that pass a given point per second, inversely related to wavelength. (Hz)

  • Amplitude: The height of the wave, which relates to the intensity or brightness of the light.

Least to highest energy

Radio → Microwaves → Infrared → Visible → UV → x-rays → Gamma

Long wavelength = less energy

Shorter wavelengh = more energy

Photo Electric Effect: The phenomenon where electrons are emitted from a material when it absorbs light, demonstrating the particle nature of light.(Light behaves both as a particle and as a wave)

Max Planck

• Observed colors of light being emitted (red → white) as iron heated up. As iron heated up the energy increased leading up to all the colors then eventually white. Rutherford’s model could not explain this.

• From this he developed the concept of quantized levels

• Planck’s Constant (h) - 6.626×10^-34 J s

• Energy gained or lost by an atom must be some integer multiple of the minimum energy an atom can give off (E = hv, 2hv, 3hv.. etc)

• Energy emitted in small, specific amounts is called “quanta”

• Quantum - minimum amount of energy that can be gained or lost by an atom.