Electrons 3.notebook 5.3 ヒラギノ角ゴ Physics and the Quantum Mechanical Model November 13, 2012 > 5.3 ヒラギノ角ゴLight Physics and the Quantum Mechanical Model Light > How are the wavelength and frequency of light related? > ヒラギノ角ゴLight The amplitude of a wave is the wave’s height from zero to the crest. ヒラギノ角ゴ > The wavelength , represented by λ (the Greek letter lambda), is the distance between the crests. Slide of 38 © Copyright Pearson Prentice Hall Slide of 38 1 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > 2 ヒラギノ角ゴ End Show Nov 99:15 AM 5.3 ヒラギノ角ゴLight Physics and the Quantum Mechanical Model > ヒラギノ角ゴLight The wavelength and frequency of light are inversely proportional to each other. ヒラギノ角ゴヒラギノ角ゴ > The frequency , represented by ν (the Greek letter nu), is the number of wave cycles to pass a given point per unit of time. ヒラギノ角ゴ > The SI unit of cycles per second is called a hertz (Hz). Slide of 38 © Copyright Pearson Prentice Hall Slide of 38 3 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > Nov 99:15 AM 5.3 ヒラギノ角ゴLight The product of the frequency and wavelength always equals a constant (c), the speed of light. ヒラギノ角ゴ Physics and the Quantum Mechanical Model > ヒラギノ角ゴLight According to the wave model, light consists of electromagnetic waves. ヒラギノ角ゴ > Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, Xrays, and gamma rays. > All electromagnetic waves travel in a vacuum at a speed of 2.998 ⋅ 108 m/s. Slide of 38 © Copyright Pearson Prentice Hall Nov 99:15 AM 4 ヒラギノ角ゴ End Show 5 ヒラギノ角ゴ End Show Slide of 38 © Copyright Pearson Prentice Hall 6 ヒラギノ角ゴ End Show Nov 99:15 AM 1 Electrons 3.notebook 5.3 Physics and the Quantum Mechanical Model November 13, 2012 > 5.3 ヒラギノ角ゴLight When sunlight passes through a prism, the different frequencies separate into a spectrum of colors. > In the visible spectrum, red light has the longest wavelength and the lowest frequency. > ヒラギノ角ゴLight The electromagnetic spectrum consists of radiation over a broad band of wavelengths. Sunlight consists of light with a continuous range of wavelengths and frequencies. ヒラギノ角ゴヒラギノ角ゴ > Physics and the Quantum Mechanical Model Slide of 38 © Copyright Pearson Prentice Hall Slide of 38 7 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 ヒラギノ角ゴ Physics and the Quantum Mechanical Model > 8 ヒラギノ角ゴ End Show Nov 99:15 AM ヒラギノ角ゴAtomic Spectra 5.3 Physics and the Quantum Mechanical Model > ヒラギノ角ゴAtomic Spectra Atomic Spectra What causes atomic emission spectra? When atoms absorb energy, electrons move into higher energy levels. These electrons then lose energy by emitting light when they return to lower energy levels. ヒラギノ角ゴ Slide of 38 © Copyright Pearson Prentice Hall Slide 9 ヒラギノ角ゴ End Show of 38 © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > Nov 99:15 AM ヒラギノ角ゴAtomic Spectra A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors. ヒラギノ角ゴ 5.3 Physics and the Quantum Mechanical Model > ヒラギノ角ゴAtomic Spectra When light from a helium lamp passes through a prism, discrete lines are produced. ヒラギノ角ゴ Slide of 38 © Copyright Pearson Prentice Hall Nov 99:15 AM 10 ヒラギノ角ゴ End Show 11 ヒラギノ角ゴ End Show Slide of 38 © Copyright Pearson Prentice Hall 12 ヒラギノ角ゴ End Show Nov 99:15 AM 2 Electrons 3.notebook 5.3 Physics and the Quantum Mechanical Model November 13, 2012 > ヒラギノ角ゴAtomic Spectra The frequencies of light emitted by an element separate into discrete lines to give the atomic emission spectrum of the element. 5.3 ヒラギノ角ゴ Mercury ヒラギノ角ゴ Physics and the Quantum Mechanical Model > ヒラギノ角ゴAn Explanation of Atomic Spectra An Explanation of Atomic Spectra How are the frequencies of light an atom emits related to changes of electron energies? Nitrogen Slide Slide of 38 © Copyright Pearson Prentice Hall of 38 13 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > 14 ヒラギノ角ゴ End Show Nov 99:15 AM ヒラギノ角ゴAn Explanation of Atomic 5.3 Physics and the Quantum Mechanical Model Spectra > ヒラギノ角ゴAn Explanation of Atomic Spectra In the Bohr model, the lone electron in the hydrogen atom can have only certain specific energies. ヒラギノ角ゴヒラギノ角ゴ > When the electron has its lowest possible energy, the atom is in its ground state. The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron. ヒラギノ角ゴ > Excitation of the electron by absorbing energy raises the atom from the ground state to an excited state. > A quantum of energy in the form of light is emitted when the electron drops back to a lower energy level. Slide Slide of 38 © Copyright Pearson Prentice Hall of 38 15 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > Nov 99:15 AM ヒラギノ角ゴAn Explanation of Atomic 5.3 Spectra The three groups of lines in the hydrogen spectrum correspond to the transition of electrons from higher energy levels to lower energy levels. ヒラギノ角ゴヒラギノ角ゴ Physics and the Quantum Mechanical Model > ヒラギノ角ゴQuantum Mechanics Quantum Mechanics How does quantum mechanics differ from classical mechanics? Slide of 38 © Copyright Pearson Prentice Hall Slide 17 ヒラギノ角ゴ End Show of 38 © Copyright Pearson Prentice Hall Nov 99:15 AM 16 ヒラギノ角ゴ End Show 18 ヒラギノ角ゴ End Show Nov 99:15 AM 3 Electrons 3.notebook 5.3 Physics and the Quantum Mechanical Model November 13, 2012 > ヒラギノ角ゴQuantum Mechanics 5.3 Physics and the Quantum Mechanical Model > ヒラギノ角ゴQuantum Mechanics Today, the wavelike properties of beams of electrons are useful in magnifying objects. The electrons in an electron microscope have much smaller wavelengths than visible light. This allows a much clearer enlarged image of a very small object, such as this mite. In 1905, Albert Einstein successfully explained experimental data by proposing that light could be described as quanta of energy. ヒラギノ角ゴヒラギノ角ゴヒラギノ角ゴ > The quanta behave as if they were particles. > Light quanta are called photons. In 1924, De Broglie developed an equation that predicts that all moving objects have wavelike behavior. Slide of 38 © Copyright Pearson Prentice Hall Slide of 38 19 ヒラギノ角ゴ End Show © Copyright Pearson Prentice Hall Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model > 20 ヒラギノ角ゴ End Show Nov 99:15 AM ヒラギノ角ゴQuantum Mechanics 5.3 Physics and the Quantum Mechanical Model > ヒラギノ角ゴQuantum Mechanics The Heisenberg uncertainty principle states that it is impossible to know exactly both the velocity and the position of a particle at the same time. ヒラギノ角ゴ Classical mechanics adequately describes the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves. ヒラギノ角ゴ > This limitation is critical in dealing with small particles such as electrons. > This limitation does not matter for ordinarysized object such as cars or airplanes. Slide of 38 © Copyright Pearson Prentice Hall 21 ヒラギノ角ゴ End Show Nov 99:15 AM 5.3 Physics and the Quantum Mechanical Model ヒラギノ角ゴヒラギノ角ゴ > Slide of 38 © Copyright Pearson Prentice Hall 22 ヒラギノ角ゴ End Show Nov 99:15 AM ヒラギノ角ゴQuantum Mechanics The Heisenberg Uncertainty Principle Slide of 38 © Copyright Pearson Prentice Hall 23 ヒラギノ角ゴ End Show Nov 99:15 AM 4