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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
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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
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)
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 particle h = 6.6262 x 10-34 Jxs (Plank’s Constant)