CHM135H1 Lecture Notes - Lecture 3: Current Meter, Work Function, Photon
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13 Sep 2018
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CHM135 – LECTURE 2: Electronic Structure of Matter
September 12, 2018 (Relevant Reading – Chemistry 7ed McMurry/Fay/Robinson, Chapter 5)
Chemistry
- Study of composition, properties, and transformations of matter
Chapter 5: Electronic Structure of Atoms
- Electronic structure can be studied by looking at the interaction between electromagnetic
radiation and matter
- Electromagnetic Radiation
o Any form of energy travelling as waves through space (e.g. radio waves, light,
microwaves
o All travel (in a vacuum) at speed of light (c = 3.00 x 108 m/s)
o Waves are characterized by:
▪ Wavelength (𝞴, lambda): distance between 2 peaks or troughs
▪ Frequency (𝑣, nu): number of waves per second that pass through a given
point; Units are cycles/s, s-1 , Hz
▪ Amplitude (a): height of peak, related to intensity of light
▪ c = 𝑣 𝞴
▪ A wave diagram shows how many cycles of waves you would see in a
given time; you can use a diagram and the given formula to calculate a
desired characteristic
▪ E.g. with visible light, wave with greater amplitude appears brighter
- Electromagnetic Spectrum
o Which wavelength of light has a higher frequency? Violet (390nm) or Red
(760nm)?
▪ Violet is near the left side of the visible spectrum while Red is near the
right end of the visible spectrum; as wavelength increases, frequency
decreases
▪ Red has a higher wavelength, so it’ll have a lower frequency than violet
o Before 1900’s
▪ Matter: discrete particles with determinate mass, position, etc.
▪ Light: continuous waves
• Undergoes Diffraction
• Undergoes Interference
o Constructive interference occurs when two waves in the
same phase are added together → results in a new wave
with a bigger trough
o Destructive interference occurs when two waves not in the
same phase are added together → results in a cancellation
of the wave (assuming the two waves had the same
amplitude)