Waves and light

Electronic Transitions Light can be absorbed or transmitted by atoms

Subatomic Particles All subatomic particles, and light act as both particles and waves Referred to as ‘wave-particle duality’ Davisson and Germer first performed the ‘double slit experiment’ in 1932 which proved this

Double Slit Experiment

Light is Electromagnetic Radiation As light propagates (travels) it emits both an electric field and a magnetic field We call light ‘electromagnetic radiation’

Light as Particles We can think of light, acting as a particle, as a photon (or particle of light) The photon is massless, and travels at the speed of light (2.998x108 m/s)

Heisenberg Uncertainty Principle It is impossible to know the position and momentum of subatomic particles simultaneously

Electromagnetic Radiation Raging Martians Invaded Venus Using X-Ray Guns Ronald McDonald Is a Very Ugly eXceptional Guy

Parts of a Wave Amplitude (A) – height of a wave Wavelength (λ) – how long the wave is (distance between crests) Crest – top part of a wave Trough – bottom of a wave Frequency (ν) – how many wavelengths pass through a point per unit time (1/s)

Wave Equations The speed of a wave (for light c, c = 2.998x108 m/s) equals the wavelength times the frequency c = λ*ν The energy of a wave (E) equals Planck’s constant (h, h=6.626x10-34 Js) times the frequency E = h*ν

Wave Equation Proportionalities For the Equations: c = λ*ν Wavelength is inversely proportional to frequency E = h*ν Energy is proportional to frequency E = h * c / λ Energy is also inversely proportional to wavelength

Wave Equation Proportions You Try If the energy of an electromagnetic wave decreases, what happens to the wave’s frequency?

If the frequency of an electromagnetic wave halves, what happens to the wave’s wavelength? If the wavelength of an electromagnetic wave doubles, what happens to the wave’s energy?

You Try Wave Equations Calculate the wavelength of yellow light (ν=5.09x1014 1/s) Calculate the Energy of a yellow light wave If the wavelength of an electromagnetic wave is 600 nm, what is that wave’s energy?

Atomic Spectra When an electron transitions to a higher energy level, light is absorbed When an electron transitions to a lower energy level, light is given off or transmitted

Emission of Light Results in Atomic Spectra

Rydberg Equation Created by Johannes Rydberg who wanted to find the relationship between spectral lines in atomic spectra Equation used to predict the wavelength of light for a given energy transition This equation works for 1 electron elements, but not so well for multiple electron elements

Rydberg Equation cont’d Rydberg noticed an interesting relationship between the energy levels of electrons and a resulting photon RH is the Rydberg constant = 1.09737… x10-7 1/m n‘s are energy levels, where n2>n1

Rydberg You Try What is the wavelength for light given an electronic transition between the 2nd and 3rd energy levels?