Warm Up

Write the correct answers for the following:

1) 2.00 x 10-4 m = __________m 2) 1.23 x 10-7 m = __________nm

Warm Up

Write the correct answers for the following:

1) 2.00 x 10-4 m = __________m 2) 1.23 x 10-7 m = __________nm

Answers: 200. m & 123 nmThink: 1) reduce 10-4 by two places & increase 2.00 two places (the resulting

number is still the same size!) 2) reduce 10-7 by two places & increase 1.23 two places to preserve the size.

THE WAVE NATURE OF LIGHT

Terms to Learn-Electromagnetic Radiation (EMR)A form of energy exhibiting wave-like behavior as it travels through space

Neely’s Chemistry

THE WAVE NATURE OF LIGHT

Electromagnetic Radiation (EMR)

Examples: visible light; microwaves; radio waves; infrared radiation; ultraviolet radiation; X-Rays; gamma rays

Neely’s Chemistry

THE WAVE NATURE OF LIGHT

Terms to Learn-Wavelength (, greek letter “lambda”)The shortest distance between equivalent points on a continuous wave. (fig 5.2)Usually expressed in m, cm, m or nm Neely’s Chemistry

THE WAVE NATURE OF LIGHT

Standing Wave (See Fig 5-2)

Neely’s Chemistry

Amplitude

The wave’s height from origin to a crest, or from origin to a trough

The higher the amplitude, the brighter the light or emr.

Frequency (, the greek letter “nu”)

The number of waves passing a given point in one second. . (Fig 5.3)

The greater the frequency, the greater the energy.

Frequency Units: cps; 1/s or s-1; Hz = 1/s “Hertz”

Useful Conversions:

CHANGE MULT. BYm to nm 109

m to m 106

Remember: G ||| M ||| k h da (m) d c m ||| ||| n

THE CONNECTION betweenfrequency & wavelength

c = speed of light c = 3.0 x 108 m/s

c =

THE CONNECTION betweenfrequency & wavelength

c = 3.0 x 108 m/s

1. A red light is found to have a wavelength of 650 nm. What is the frequency of this radiation?

(Note: nm = 10-9m)

c =

THE CONNECTION betweenfrequency & wavelength

c = 3.0 x 108 m/s

2. A violet light has a frequency of 7.32 x 1014 Hz. What is the wavelength of this radiation? (Note: nm = 10-9m)

c =

THE CONNECTION betweenfrequency & wavelength

c = 3.0 x 108 m/s

3. A green light has a wavelength of 4.90 x 10-9 m. What is the speed of this electromagnetic wave?

c =

Which wave has the higher freqency ()? What happens to the frequency as the

wavelength increases? What is this called (in math)?

THE EMR SPECTRUM

Increasing ENERGYRadio

microwave InfraredVisible

UVX-Rays

gamma rays

SEE FIG 5-5 p 120 in TextbookNeely’s Chemistry

THE END