The shorter the wavelength ( ), the higher the frequency ( ). Energy of the wave increases as frequency increases.

Electromagnetic spectrum Converting from wavelength (  to frequency (   Ex: What is the frequency of a 400 nm EM wave? = c/ = (3.00 x 10 8 m/s) / (4.00 x m) = 7.50 x Hz c =

Ground state: electron is at its lowest possible energy level + + n = 1 n = 2 n = 3 n = 4 n = 5 Excited state: electron is above the lowest possible energy level H 1 1 Photon absorbed Photon emitted

Hydrogen Atomic emission spectrum of hydrogen

Bohr atomic orbit Quantum number Orbit radius (nm) Atomic energy level Relative Energy Firstn = E1E1 Secondn = E 2 = 4E 1 Thirdn = E 3 = 9E 1 Fourthn = E 4 = 16E 1 Fifthn = E 5 = 25E 1 Sixthn = E 6 = 36E 1 Seventhn = E 7 = 49E 1 Page 127 in text For emission:  E = E higher – E lower = E photon = h = hc/ = frequency (Hz)h = Planck’s constant (6.63 x J·s) = wavelength (m) c = speed of light (3.00 x 10 8 m/s)

Examples 1. What is the energy of a green photon having a wavelength of 514 nm? E = hc/ = (6.626 x J·s)(3.00 x 10 8 m/s) 5.14 x m = 3.87 x J 2. What is the frequency of the photon in #1? = c/ = (3.00 x 10 8 m/s) / (5.14 x m)= 5.84 x Hz 3. What is the frequency of a photon that has an energy of 3.31 x J? = E/h = (3.31 x J) / (6.626 x J·s)= 5.00 x 10 6 Hz (use c = ) (use E = h )

Some people say I have a dual personality! Hi, I’m a photon!

Wave nature of light

Diffraction: the bending of waves around an object Diffraction around an obstacle Diffraction through an opening Diffraction around a corner The amount of diffraction that occurs depends upon the size of the obstacle or opening and the wavelength of the incident wave

Electromagnetic waves Both electrical charges and magnets have fields around them. An electromagnetic wave is a double transverse wave that consists of both an electric and a magnetic field wave

Electromagnetic waves are transverse waves because the electric and magnetic fields vibrate in a direction perpendicular to the direction of travel.

Photoelectric Effect e e e e Na metal V ‘Particles’ of light are called photons

If light can have characteristics of BOTH particles and waves… …can particles of matter also behave like waves? De Broglie’s equation h = 6.63 x J·s m = mass in kg v = velocity in m/s

6.0 x kg 2.8 x 10 4 m/s e 9.1 x kg 3.0 x 10 8 m/s 5.7 x kg 53 m/s (Venus Williams, 1998) h = 6.63 x J·s m = mass in kg v = velocity in m/s What is the wavelength of these three ‘particles’?