University:
University of Pennsylvania
Course:
CHEM 1022 | General Chemistry II
Academic year:

2022
Views:

199

Pages:

17
Author:

Carissa Thomas

Chemistry Chapter 5 Wave Nature of Light Visible light is a type of electromagnetic radiation It is a form of energy which exhibits wavelike behavior as it travels through space Other examples of electromagnetic radiation include microwaves, x-rays and radio waves Electromagnetic Radiation Made of photons A photon is a discrete packet of electromagnetic energy The Energy can be calculated as either E=hv or E=hc/λ Characteristics of Waves Wavelength (λ): Lambda is the shortest distance between equivalent points on a continuous wave, it is measured from crest to crest and is usually expressed in meters Frequency (v): Nu is the number of waves that pass a given point per second. One Hertz (Hz: The SI unit of frequency) equals one wave per second. Wave Characteristics Amplitude is the waves height from origin to crest Wavelength and frequency do not affect the amplitude Wavelength and frequency are inversely proportional (as one increases the other decreases) Electromagnetic Wave Relationship c = λv c = the speed of light in a vacuum λ = the wavelength v = the frequency All electromagnetic waves, including visible light, travel at a speed of 3.00 x 108 m/s in a vacuum Relationships c = λν v = c/λ λ = c/v MHz = 106Hz Hz = s-1 nm = 10-9m c = 3.00 x 108m/s Wavelength Electromagnetic Waves The visible light spectrum is from about 350nm (violet) to 800nm (red) Blue is around 450nm Below 350nm is ultraviolet above 800nm is infra-red Calculations A radio station broadcasts at 122.0 MHz. Calculate the wavelength of this frequency. Calculate the frequency of a radiation which is 614 nm in length. What color is this radiation? Particle Nature of Light In addition to exhibiting wavelike behaviors, light also behaves as a particle As a result, when objects are heated they will only emit electrons when light of a specific frequency shines on them Example: Iron is gray at room temperature, glow red when heated, then orange and finally blue at excessively high temperature Particle Nature The different frequencies of the colors cannot be explained by the wave nature of light, they are explained by the gain or loss of energy This energy is in the form of a Quantum A Photon is a particle which carries a quantum of energy The energy of the photon depends on the frequency Atomic Emission Spectra Neon lights are explained by the wave model of light The light is produced by passing electricity through the gas If the light neon emits is passed through a prism we don’t get the full range of colors like we do with visible light Instead we observe discrete lines which correspond to the radiation emitted by neon Separation of light by a prism according to wavelength Continuous, emission, and absorption spectra

Chapter 5 Electromagnetic Radiation

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