The Development of a New Atomic Model Rutherford- did not explain how the atom’s negatively charged particles are distributed in the space surrounding it’s positively charged nucleus.
The New Atomic Model Researcher used investigations into the absorption and emission of light Studies revealed a relationship beteen light an atom’s electrons New understanding about the nature of energy, matter, and atomic structure.
Properties of Light Before 1900, light was thought to behave solely as a wave Wavelike description It is type of electromagnetic radiation Forms part of the electromagnetic spectrum Significant wavelike motion characterized by wavelength and frequency Wavelength (λ) is the distance between corresponding points on adjacent waves. Frequency (v) is the number of waves that pass a specific point in a given time, usually one minute.
Frequency and wavelength are mathematically related to each other c=λv c is the speed of light, a constant There for λ, wavelength in m, is inversely proportional to v, frequency in s-1. As wavelength decreases frequency increases and vice versa
The Photoelectric Effect The photoelectric effect refers to the emission of electron when light is shines on a metal.
The Photoelectric Effect The mystery was….. No electron would be emmited if the lights frequency (v) was below a certain minimum. No matter how intense (W) the light was. Wave theory state that light of any frequency could supply enough energy to eject an electron.
The Particle Description of Light Max Planck (1900 German Physicist) Studied emission of light by hot objects He proposed the hot objects do not emit electromagnetic energy continuously (as would be expected if all we were dealing with was a wave)
The Particle Description of Light Quantum- a measure of energy that is the minimum quantity of energy that can be lost or gain by an atom Planck proposed a relationship between a quantum of energy and the frequency of radiation E=hv E= energy in joules, v is frequency (s-1), h= a fundamental physical constant now know as Planck’s constant = 6.626x 10 -34
The Duality of particles and waves Albert Einstein expanded on Planck’s work and proposed a radical idea Electromagnetic radiation has a dual wave-particle nature While like light act like a wave It is a stream of particles Each particle carries a quantum of energy These particles are called photons These particles have zero mass but carry a quantum of energy
This explained the photoelectric effect Einstein explained Electromagnetic radiation is only absorbed by matter in whole numbers In order for an electron to be rejected from the surface of the metal it must be struck by a single photon possessing at least a minimum energy required to knock the electron off. Every metal has a different frequency
Home work Pages 124-125 #1-25 Complete sentences If it is a multiple choice problem, select the letter choice them write a true complete sence out of the question and the choice: DO NOT COPY THE QUESTIONS If it is a calculation, show equation used and ALL work Have a great Thanksgiving!!!