Presentation on theme: "Light as a Wave OBJECTIVES:"— Presentation transcript:
1 Light as a WaveOBJECTIVES:Describe the relationship between the wavelength and frequency of light.
2 Electrons and LightAfter Bohr’s model, the mystery of the atom was the nature of the electron cloud.The study of light – particularly the wave nature of light – played a critical role in probing the nature of the electron cloud.
3 Light and Energy are Linked Energy travels through space as light waves.These Light waves are known as Electromagnetic Radiation (EMR)EMR – defined as a form of energy that exhibits wavelike behavior as it travels trough space.
4 Types of EMR Visible Light is one type of EMR Others include x-rays, microwaves, radiowaves, gamma rays, ultraviolet waves, infrared waves.All electromagnetic radiation travels at this same rate.This rate is the speed of light (c)c = 3.0 x 108 m/sec
6 Basic Properties of Waves Wavelength (λ- lambda) – distance between two crests of a wave. Units are usually meters.Frequency (f or (nu) )- the number of wave cycles that pass a given point per unit time (usually seconds)Units are sec-1 = Hertz
7 Parts of a waveCrestWavelengthAmplitudeOriginTrough
8 Wavelength and Frequency Are inversely relatedAs one goes up the other goes down.c = or c = fc = speed of light = 3.0 x 108m/s
9 As frequency decreases, wavelength increases. As frequency increases, the wavelength decreases.
10 Different frequencies of light are different colors of light. There is a wide variety of frequenciesThe whole range is called a spectrum
11 EM Spectrum HIGH ENERGY LOW ENERGY R O Y G. B I V red orange yellow greenblueindigoviolet
12 The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.Equation: E = hfE = Energy, in units of Joules (kg·m2/s2)(Joule is the metric unit of energy)h = Planck’s constant (6.626 x J·s)f = frequency, in units of hertz (hz, sec-1)
13 Low ENERGY Waves = Long Wavelength Low Frequency High ENERGY Waves = Wavelength TableHigh ENERGYWaves=ShortWavelengthHigh Frequency
21 Calculating Wavelength of an EM Wave Electrons in Atoms: Basic ConceptsTopic9Calculating Wavelength of an EM WaveMicrowaves are used to transmit information.What is the wavelength of a microwave having a frequency of 3.44 x 109 Hz?Solve the equation relating the speed, frequency, and wavelength of an electromagnetic wave for wavelength (λ).
22 Calculating Wavelength of an EM Wave Electrons in Atoms: Basic ConceptsTopic9Calculating Wavelength of an EM WaveSubstitute c and the microwave’s frequency, n, into the equation. Note that hertz is equivalent to 1/s or s–1.
23 Examples c = λf or f = c/λ f = 3.0 x 108m/s 4.2 x 10-5 m 2) What is the frequency of red light with a wavelength of 4.2 x 10-5 m?3) What is the energy of the photon above?c = λf or f = c/λf = x 108m/s4.2 x 10-5 m= 7.1 x 1012 sec-1E = hfE = (6.626 x J sec) (7.1 x 1012 sec-1)E = 4.73 x Joules