1. Section 5.1 Light and Quantized Energy

2. Objectives Compare the wave and particle models of light Compare the wave and particle models of light Define a quantum of energy and explain how it is related to an energy change of matter Define a quantum of energy and explain how it is related to an energy change of matter Contrast continuous electromagnetic spectra and atomic emission spectra Contrast continuous electromagnetic spectra and atomic emission spectra

3. Light and Quantized Energy Problems with Rutherford Problems with Rutherford –Twentieth century scientists found the Rutherford model of the atom incomplete because it did not explain how the electrons were arranged in the atom. –Scientists observed that consecutive elements like chlorine, argon, and potassium have similar number of protons and electrons, but VERY different chemical properties.

4. Light and Quantized Energy Wave Nature of Light Wave Nature of Light –Electromagnetic radiation (ER) is a form of energy that exhibits wavelike behavior as it travels through space. –Examples: visible light, microwaves, x-rays, and radio waves.

5. Light and Quantized Energy Characteristics of waves Characteristics of waves –wavelength, frequency, amplitude, and speed –Wavelength,, is the shortest distance between equivalent points on a continuous wave.  Measure in nm (nanometers) –Frequency,, is the number of waves that pass a given point per second.  Measured in Hz (Hertz)

6. Light and Quantized Energy Characteristics of waves (cont.) Characteristics of waves (cont.) –Amplitude: wave’s height from the origin to a crest, or from the origin to a trough. –The speed of light = c = 3.0X10^8 m/s –Wavelength and Frequency are related to the speed of light by the following equation.

7. Light and Quantized Energy

8. Wave Nature of Light Wave Nature of Light –The electromagnetic (EM) spectrum is a continuous spectrum of different types of ER. –We say the EM spectrum is continuous because there is no portion that does not correspond to a unique wavelength and frequency.

9. Light and Quantized Energy

10. Calculating wavelength/frequency Calculating wavelength/frequency –Example P.121 –Assignment P.121 #1-4