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Chapter 4

- The Electromagnetic Spectrum
- Part 1

Demonstration

- Gas spectral tubes
- Neon Argon

Visible Light

- Part of the Electromagnetic Spectrum

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All types of electromagnetic energy move in waves.

- Light and sound move by waves.
- Light moves at
- 3 x 108 m/s
- Sound moves at
- 340 m/s
- 1 mile 1609 m

All types of electromagnetic energy move in waves.

- Light moves at
- 3 x 108 m/s
- Sound moves at
- 340 m/s
- Is sound a form of electromagnetic radiation?

Electromagnetic Waves

- Properties of waves include speed, frequency and

wavelength - All electromagnetic waves including light travel

at a speed of 3 x 108 m/s.

Wavelength (?)

Measured in units of length m, nm, A

º

Frequency (?)

Measured in cycles/second hertz (Hz)

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Visible Light

Why do we want to understand electromagnetic

radiation (light)?

- Well, for one thing, it may someday allow us to

become invisible.

Electromagnetic Radiation

- For all waves ? ? c
- c the speed of light 3.00 x 108 m/s

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

- 665 nm 665 x 10-9 m

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

- 665 nm 665 x 10-9 m
- c ? ?

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz

A photon of red light has a wavelength of 665 nm.

What is the frequency of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz
- ? 4.51 x 1014/s or Hz

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

- 7.25 x 1020 Hz 7.25 x 1020/s

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

- 7.25 x 1020 Hz 7.25 x 1020/s
- c ? ?

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

- 7.25 x 1020 Hz 7.25 x 1020/s
- c ? ?
- ? c ? 3.00 x 108 m/s 7.25 x 1020/s

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

- 7.25 x 1020 Hz 7.25 x 1020/s
- c ? ?
- ? c ? 3.00 x 108 m/s 7.25 x 1020/s
- ? 4.137931 x 10-13 m

An x-ray has a frequency of 7.25 x 1020 Hz. What

is the wavelength?

- 7.25 x 1020 Hz 7.25 x 1020/s
- c ? ?
- ? c ? 3.00 x 108 m/s 7.25 x 1020/s
- ? 4.137931 x 10-13 m
- ? 4.14 x 10-13 m

Energy of Electromagnetic Radiation

- For all waves E h ?
- h 6.63 x 10-34 J s or J/Hz

A photon of red light has a wavelength of 665 nm.

What is the energy of this light?

A photon of red light has a wavelength of 665 nm.

What is the energy of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz
- ? 4.51 x 1014/s or Hz

A photon of red light has a wavelength of 665 nm.

What is the energy of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz
- ? 4.51 x 1014/s or Hz
- E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)

A photon of red light has a wavelength of 665 nm.

What is the energy of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz
- ? 4.51 x 1014/s or Hz
- E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)
- E 2.99013 x 10-19 J

A photon of red light has a wavelength of 665 nm.

What is the energy of this light?

- 665 nm 665 x 10-9 m
- c ? ?
- ? c ? 3.00 x 108 m/s 665 x 10-9 m
- ? 4.511278 x 1014/s or Hz
- ? 4.51 x 1014/s or Hz
- E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)
- E 2.99013 x 10-19 J 2.99 x 10-19 J

An x-ray has a frequency of 7.25 x 1020 Hz. What

is its energy?

An x-ray has a frequency of 7.25 x 1020 Hz. What

is its energy?

- E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)

An x-ray has a frequency of 7.25 x 1020 Hz. What

is its energy?

- E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)
- E 4.80675 x 10-13 J

An x-ray has a frequency of 7.25 x 1020 Hz. What

is its energy?

- E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)
- E 4.80675 x 10-13 J
- E 4.81 x 10-13 J

wavelength, frequency and energy

Red Light

- ? 665 x 10-9 m
- ? 4.51 x 1014 Hz
- E 2.99 x 10-19 J

- ? 4.14 x 10-13 m
- ? 7.25 x 1020 Hz
- E 4.81 x 10-13 J

X-ray

Wavelength, frequency and energy

- Wavelength and frequency have an inverse

relationship. - Energy and frequency have a direct relationship.
- Electromagnetic radiation with a shorter

wavelength will have a higher frequency and

higher energy. - Electromagnetic radiation with a longer

wavelength will have a lower frequency and lower

energy.

Homework

- Chapter 4 Worksheet 2 (due in two days)