## Presentation on theme: "Light CHEM HONORS. The Nature of light Light is electromagnetic radiation, a wave created of oscillating, support perpendicular electric and also magnetic."— Presentation transcript:

You are watching: The number of cycles that pass through a stationary point is called

1 light CHEM HONORS

2 The Nature of light Light is electromagnetic radiation, a wave created of oscillating, support perpendicular electric and magnetic fields propagating through space. In a vacuum, light travels in ~ a consistent speed the 3.00 x 10 8 m/s

3 Characterization the a wave Amplitude – the vertical elevation of a stakes ( or depth of a trough) The higher the amplitude the much more intense or bright the irradiate is Wavelength ( ) – distance between adjacent crests (commonly measured in m, μm, or nm) Waves through a huge amplitude and also a quick wavelength room the many energetic

4 Frequency Frequency ( ) – the variety of cycles that pass through a stationary suggest in a given period of time. The units space s -1 (cycles/s) or Hz ( 1 cycle/s) The frequency is directly proportional to the speed at i m sorry the tide is traveling and is inversely proportional to the wavelength ( ) = c /

5 Checkpoint calculate the wavelength (in nm) of the red irradiate emitted through a barcode scanner that has actually a frequency the 4.62 x 10 14 s -1. = c /

6 Electromagnetic Spectrum

7 Interference

8 Diffraction

9 Interference from two Slits

10 The particle Nature of light After the discovery of the diffraction the light, irradiate was thought to be completely a tide phenomenon. But a variety of discoveries lugged this classical view right into question – mostly the photoelectron result

11 The Photoelectron effect The observation that countless metals emit electrons once light shines ~ above them. Classical electromagnetic theory would attribute the amplitude the the wave (intensity of the beam) together the source of the emitted electron The experimental results go not support this theory – high frequency, short intensity lights to be still create electrons The results proved that there was a threshold frequency In various other words, short frequency irradiate does no emit electrons whereas high frequency light does.

12 The Photoelectric impact Einstein used quanta to explain the photoelectric effect. Every metal has actually a different energy in ~ which the ejects electrons. At reduced energy, electrons are not emitted. He concluded that energy is proportional to frequency: E = h where h is Planck’s constant, 6.626 10 −34 J ∙ s.

13 The Nature that Energy—Quanta Max Planck explained it by assuming that power comes in packets dubbed quanta (singular: quantum). Planck’s constant – the power of every photon in terms of the photon’s frequency.

14 Checkpoint A nitrogen gas laser has a wavelength that 337 nm, what is the energy of the laser? E = h = c / c = 3.0 x 10 8 m/s h = 6.626 x 10 -34 J s

15 atom Spectroscopy and the Bohr version Another mystery in the beforehand twentieth century involved the emission spectra it was observed from energy emitted by atoms and molecules.

16 constant vs. Heat Spectra for atoms and also molecules, one does not observe a continuous spectrum (the “rainbow”), as one it s okay from a white light source. Only a line spectrum of discrete wavelength is observed. Each element has a unique line spectrum.

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18 The Hydrogen Spectrum Johann Balmer (1885) found a basic formula relating the 4 lines come integers. John Rydberg progressed this formula.

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19 questions (Read Pages 306 – 309) 1.) What reasons spectral lines? prize on the atomic level and use Planck’s and Bohr’s ideas 2.) Why do elements have more than one spectral line? Why aren’t over there infinitely many lines? define the significance, with respect to proving or disproving the atomic model, of there not being infinite numerous lines 3.) according to Bohr’s atom model, where might an atom’s electrons be found? 4.) What walk it median for electron to become “excited”?

20 concerns 5.) State the equation that is provided to determine the power content of a packet of light of particular frequency. If only the wavelength of irradiate is known, what extr equation is needed? 6.) What type of energy emission accompanies the return the excited electrons to your ground state? 7.) What is the frequency of a photon of light that has actually a wavelength of 692 nm? What is the power of one mole of these photons (in kJ/mol)? 8.) just how does a fire test support the quantum mechanical model of the atom? Why are different metals different colors? 9.) describe the difference in between emission and also absorption spectra?