Lesson: Electcromagnetic Spectrum (EMS)

Parts of a wave

Wavelength – Distance between two corresponding points on successive waves.Amplitude – measure of a wave’s “strength” (height of crest or trough).

The Wave-like Electron

Louis deBroglie

The electron propagates through space as an

energy wave. To understand the atom, one must understand

the behavior of electromagnetic waves.

Electromagnetic Wave – An electric wave and magnetic wave moving at right angles to each other.

Electromagnetic Spectrum – Arrangement of all forms of electromagnetic radiation in order of frequency and wavelength.

• Frequency (ν): number of wavelengths that pass a certain point in a given amount of time.

- units are Hertz (Hz)

• If these 2 waves are traveling at equal speeds, which wave will have more wavelengths cross the finish line in one minute?

FIN

ISHlow frequency

high frequency = short wavelength

= long wavelength

• If these 2 waves are traveling at equal speeds, which wave will have more wavelengths cross the finish line in one minute?

FIN

ISHlow frequency

high frequency = short wavelength

= long wavelength

Left Side Practice

1) Pick a type of wave on the EMS (not visible light). 2) Draw a pic of that wave and label the crest, trough, wavelength and amplitude.3) Write and answer these questions:• Does it have a greater wavelength than visible

light?• Does it have a higher frequency than visible

light?• Does it have more or less energy than visible

light?

3) Write and answer these questions:Does it have a greater wavelength than visible light?Does it have a higher frequency than visible light?Does it have more or less energy than visible light?

Warm Up 10/17

Which has the greatest: Wavelength? Frequency? Energy?

• Wavelength (λ) and frequency (f) are inversely related.

• All waves on the EMS travel at the speed of light (c).

c = λ x f

• c = speed of light = 3.00 x 108 m/s.

o to solve for λ …c

λ = f

o to solve for f … c

f =λ

Practice Calculate the υ of a wave that has a wavelength of 5.00 x 10-6 m.

c

ν =λ

ν=

=ν Hz

Does this radiation have a shorter or longer λ than red light?

What is the wavelength of radiation with a frequency of 1.50 x 1013 Hz?

c

λ = ν λ =

λ =

Practice

Calculate the wavelength of yellow light emitted by a sodium lamp, if the frequency of the radiation is

5.10 x 1014 Hz.

On Your Own Practice

* Hint: Be sure you set up the right equation. Ask yourself: which variable am I solving for?

Create Your Own Problem Create a problem so that you have to

solve for frequency (f). To do that, just make up a wavelength (between 10 and 10 . Solve it for yourself, then find one other person to solve it and check your work. Be sure to write your question as a word problem.

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