Section 11.1 Atoms and Energy 1.To review Rutherford’s model of the atom 2.To explore the nature of electromagnetic radiation 3.To see how atoms emit light Objectives

Section 11.1 Atoms and Energy A. Rutherford’s Atom …….but there is a problem here!!

Section 11.1 Atoms and Energy When were you last exposed to electromagnetic radiation?

Section 11.1 Atoms and Energy What is the nature of electromagnetic radiation? How are the types of electromagnetic radiation different? B. Energy and Light –Light can be modeled as a wave, like a wave in water

Section 11.1 Atoms and Energy How are the types of light different? B. Energy and Light –Wavelength, λ (Greek letter “lambda”) units - m –Frequency, ν (Greek letter “nu”) units - s -1 or Hertz (Hz) –Amplitude, peak height – relates to energy in wave –Speed, c : velocity of light in a vacuum is 3x10 8 m.s -1 c = ν. λ ν ( s -1 ) (m)

Section 11.1 Atoms and Energy Electromagnetic radiation B. Energy and Light

Section 11.1 Atoms and Energy Wavelength and Frequency of Visible Light Frequency in Terahertz (1THz = Hz) and Wavelength in Nanometers (1nm = meters)

Section 11.1 Atoms and Energy Light Sometimes Behaves in Un-wavelike Ways The Photoelectric Effect –Light shining on a metal surface can cause electrons to be separated from their atoms –Below a threshold frequency no electrons are emitted however high the intensity –At the threshold frequency electrons start to be emitted –At higher frequencies electrons have additional kinetic energy

Section 11.1 Atoms and Energy Dual nature of light – Two co-existing models B. Energy and Light –Wave –Photon – packet of energy

Section 11.1 Atoms and Energy Different photons (from light of different wavelengths) carry different amounts of energy. B. Energy and Light Energy of photon = h.ν (h is Planck’s Constant )

Section 11.1 Atoms and Energy C. Emission of Energy by Atoms Atoms can give off light –They first must receive energy and become excited. –The energy is released in the form of a photon.