CHEM101 Study Guide - Fall 2018, Comprehensive Midterm Notes - Electromagnetic Radiation, Quantum, Photon

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CHEM101
MIDTERM EXAM
STUDY GUIDE
Fall 2018
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Wave property variables:
1. Frequency: cycles per second (n)
2. Wave Length: the distance a wave travels in one cycle (l)
3. Amplitude: the height of a wave crest or the depth of a trough (the intensity / brightness of light is related to its
amplitude)
* wavelength and frequency = reciprocal relationship
Waves and Matter have different behaviours:
1. Refraction:
a. WAVE: When a wave of light enters a new medium, it causes a change of speed which causes a change
in direction known as refraction. (The angle of the refraction depends on the two media being passed
through and the wavelength of the light)
b. MATTER: matter will not refract, for example, if you throw a pebble into a pond it will continue to slow
down gradually along a curved path after it enters the water
2. Dispersion: white light separates /disperses into its component colours when it passes through a prism or
another refracting object because each incoming wave is refracted at a slightly different angle
3. Diffraction: When a wave strikes the edge of an object, it bends around it.
a. EX. if waves pass through a slit, it bends around both edges of the slit and form a semicircular wave on
the other side of the opening. When you throw matter, for example, sand at a small opening, some
particles will hit the edge while others go through the opening and continue in a narrower group.
4. Interference: when wave lights pass through two adjacent slits the nearby emerging circular waves interact
through the process of interference. Two different kind:
a. Constructive: If the crests of the waves coincide, (in phase) The amplitudes add together to form a
brighter region.
b. Destructively: If the crest coincides with the troughs, (out of phase), the amplitudes cancel to form a
darker region. The result is a diffraction pattern.
THE PHOTOELECTRIC EFFECT:
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A monochromatic light shines on a metal surface, electrons are released from the surface of the metal and
travel to the electrode, as a result, a current is produced
OBSERVATION 1: the effect only occurs above a min. threshold frequency
OBSERVATION 2: there is no time lag
Albert Einstein’s Photon Theory: light is a particle and is quantized into small packets of energy called photons
BLACK BODY RADIATION:
- When a solid object is heated to about 1000K or higher it emits visible light (smouldering coal, glowing stove
element)
- Explanation: Max Planck developed a formula; blackbodies and the atoms within them can only emit (or
absorb) certain quantities of energy
oE=nhv
E= energy of the radiation
V = frequency
N= positive integer called a quantum number
H = Planck’s Constant
- Energy is quantized (it occurs in fixed quantities rather than being continuous, each of which is called a
quantum plural: quanta)
- An atom changes its energy state by emitting or absorbing one or more quanta of energy
- Change in energy =
- Minimum change =
- Conclusion =
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CHEM101 Full Course Notes
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CHEM101 Full Course Notes
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Document Summary

Ex. if waves pass through a slit, it bends around both edges of the slit and form a semicircular wave on the other side of the opening. When you throw matter, for example, sand at a small opening, some particles will hit the edge while others go through the opening and continue in a narrower group. Interference: when wave lights pass through two adjacent slits the nearby emerging circular waves interact through the process of interference. A monochromatic light shines on a metal surface, electrons are released from the surface of the metal and travel to the electrode, as a result, a current is produced. Observation 2: there is no time lag. Albert einstein"s photon theory: light is a particle and is quantized into small packets of energy called photons. When a solid object is heated to about 1000k or higher it emits visible light (smouldering coal, glowing stove element)