1. Electromagnetic Spectrum

2. Light Phenomenon Isaac Newton (1642-1727) believed light consisted of particles By 1900 most scientists believed that light behaved as a wave.

3. The Electromagnetic Spectrum The electromagnetic spectrum represents the range of energy from low energy to high Low energy = long wavelengths & low frequency High energy = short wavelengths and high frequency

4. Visible light is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors. R ed O range Y ellow G reen B lue I ndigo V iolet ROY G BIV

5. The visible spectrum falls within the range of the Sun’s electromagnetic energy—our eyes have evolved to take greatest advantage of the available light.

6. Sodium Lights

7. Wavelengths and Frequency Wavelength = the distance between two peaks in a wave Frequency = how often a wave passes (or hits) an object High frequency = short wavelength Low frequency = long wavelength

8. Particles of light are governed by the Speed of Light Equation C = λν The frequency (v) of a wave is the number of waves to cross a point in 1 second (units are Hertz – cycles/sec or sec -1 ) Megahertz (mHz) = 1,000,000 Hz Kilohertz (kHz) = 1,000 Hz λ is the wavelength- the distance from crest to crest on a wave

9. The product of wavelength and frequency always equals the speed of light. C = λν Why does this make sense? NOTE: c is a constant value= 3.00 x 10 8 m/s

10. Calculate the wavelength of yellow light emitted from a sodium lamp if the frequency is 5.10 x 10 14 Hz can be written 5.10 x 10 14 s -1 1) List the known infoList the unknown c = 3.00 x 10 8 m/swavelength (λ) = ? cm Frequency (v) = 5.10 x 10 14 s -1 2) Rearrange the Equation and plug in the knowns c = λv λ = c v λ = 3.00 x 10 8 m/s = 5.88 x 10 -7 m 5.10 x 10 14 s -1 PROBLEMS