Chapter 5 – Electrons in Atoms text pages

HISTORY Isaac Newton thought of light as consisting of particles (1700’s) By the 1900’s most scientists believed light was a form of waves The wave model describes light consisting of electromagnetic waves

Review of Waves

ELECTROMAGNETIC RADIATION Series of waves including the visible & invisible Travels in a vacuum at 3.0 x cm/s or 3.0 x 10 8 m/s

The electromagnetic spectrum FREQUENCY DECREASING & WAVELENGTH INCR

FREQUENCY vs. WAVELENGTH Wavelength (λ) -- distance between two crests Frequency (v) -- number of waves to pass a point per unit time Speed of light (c) – constant, 3 x 10 8 m/s Frequency and wavelength have an inverse relationship c= λ v

Calculate the wavelength of the yellow light emitted by a sodium lamp if the frequency of the radiation is 5.10 x s -1. c= λ v v= 5.10 x s -1 c= 3.0 x 10 8 m/s λ=?

Who is Max Planck? studied visible emissions from hot glowing solids proposed that light was emitted in “packets” of energy called quanta (a.k.a. photons) the energy of each packet was proportional to the frequency of the light wave According to Einstein and Planck, the energy of a quantum, E = h x v Planck’s constant (h)= x J x s

Calculate the energy of a photon whose frequency is 3.55 x s -1. E = h x vh = x J x s v = 3.55 x s -1

The photoelectric effect is when electrons are emitted from a metal’s surface when light of a certain frequency shines on it. Alkali metals are particularly subject to the effect