Wave and Particle Models of Light, Quantum Energy, and Electromagnetic Spectrum

1. Section 5.1 Light and Quantized Energy

2. Objectives • 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 • Contrast continuous electromagnetic spectra and atomic emission spectra

3. Light and Quantized Energy • 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 • 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 • 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.) • 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 followingequation.

7. Light and Quantized Energy

8. Light and Quantized Energy • 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. Light and Quantized Energy • Calculating wavelength/frequency • Example P.121 • Assignment P.121 #1-4