physics and the quantum mechanical model notes. light and the atomic spectrum light is composed of...
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Physics and the Quantum
Mechanical Model Notes
Light and the Atomic Spectrum
• Light is composed of waves at different wavelengths
• The wave is composed of:– Wavelength (λ): is the distance between the crests– Frequency (ν): the number of wave cycles to pass a
point per time– Amplitude: The height of the crest from the origin
Waves
You can calculate the frequency and wavelength of light using the equation
c= λν
c = speed of light (3.0 x 1010 cm/s or 3.0 x 108 m/s)
λ = wavelength (cm or m – distance between crests)
ν = frequency (1/s or s-1 = hertz = Hz)
Electromagnetic Spectrum• Visible Light is composed of a small section of
the Electromagnetic Spectrum
• EMS- a scale of all forms of radiation that exhibit wave-like behavior as they travel through space
• Light can be broken up into a spectrum of colors (ROY G BIV)
red – orange - yellow – green – blue – indigo- violet Violet is the highest energy (shortest wavelength)
Red is the lowest energy (longest wavelength)
Electromagnetic Spectrum (EMS)
Types of Spectra
Types of Spectra
• Continuous: Produced by a hot, opaque (dense gas or solid). A RAINBOW of colors
• Emission/Dark Line: Produced by a hot, transparent gas
• Absorption: Produced by a cool, transparent gas
Atomic Emission Spectrum• Each element has its own unique emission
spectrum when it is excited
• Excitation is usually induced via heat, electricity, etc.
• Excited = move up an energy level (absorb a “quanta” of energy. When e moves back to ground state, a quanta of energy (called a PHOTON is released
Quanta = “Packet” of Energy
• Photon: “particle” of electromagnetic radiation. ZERO mass, carries a quantum (amount) of energy
• When an electrons falls back to it’s natural (non “excited state”) it’s seen a light and felt as heat
Photoelectric Effect (Solar Cells)
• Metals eject electrons called photoelectrons when light shines on them (energy not emitted continuously)
• Plank showed relationship between the intensity of light shined on metal (frequency) and amount of electrical current produce (Energy).
Plank’s Constant
E = h x v
E = radiant energy
h = 6.6262 x 10-34 Jxs (Plank’s Constant) = Energy of one photon
v = frequency of the radiation (Hz)
Frequency (v) and Energy (E) directly proportional!
De Broglie equation
• Wave-particle duality: Particles exhibit wave and particle properties (not just light but ALL matter)
λ = h / mv
m = mass of particleh = 6.6262 x 10-34 Jxs (Plank’s Constant)
Atomic Emission Spectrum