1. Electromagnetic Energy
Prepared by: Timothy John D. Matoy

2. Photons First described by ancient Greeks
Today, they are known as electromagnetic Energy
No mass, no identifiable form
They do have electric and magnetic fields that are continuously changing in sinusoidal fashion.

3. Photons
A photon is the smallest quantity of any type of electromagnetic energy.
A photon may be pictured as a small bundle of energy, sometimes called quantum.

4. James Clerk Maxwell Late in 19th century.
Showed that visible light has both electric and magnetic properties, hence the term electromagnetic energy.

5. Properties of EM Radiation
It can travel through empty space.
It travels with the speed of light.
It travels in a wave-like fashion.

6. Velocity
The velocity of all electromagnetic radiation is 3 x108 m/s or 186,000 miles per second.

7. Wavelength
The distance from one crest to another, from one valley to another, or from any point on the sine wave to the next corresponding point.

8. Frequency
Is the number of wavelength that pass a point of observation per second.

9. Wave Equation
V = λf
Velocity = wavelength x frequency

10. Electromagnetic Wave Equation
C = λf
Speed of light = wavelength x frequency

11. Practice problem
The highest energy x-ray produced at 120 kVp has a frequency of 2.50 x1019 Hz. What is the wavelength?

12. Practice Problem
What is the frequency of a certain electromagnetic wave with a wavelength of 300 cm?

13. Sample problem
The speed of sound in air is approximately 340 m/s. The highest treble tone that the person can hear is about 20 kHz. What is the wavelength of this sound?
1.7 cm

14. Electromagnetic Spectrum
The frequency range of electromagnetic energy extends from approximately 102 to 1024 Hz.
The wavelength are approximately 107 to m.

15. Electromagnetic Spectrum

16. Visible light What your eye detects
Has a wavelength of 4000 to 8000 angstroms
1 angstrom = 1.0 x10-10 m
1 nm = 1.0 x10-9 m = 10 angstrom
400 nm for violet
700 nm for red
Refraction, rainbow

17. Radiofrequency
Relatively low energy and relatively very long wavelength

18. Ionizing Radiation Gamma ray X-ray
RF and VL are identified by Frequency
Ionizing radiation is identified by energy
80 kVp – produces from 0 to 80 kVp

19. Wave-Particle Duality
Photons interact with matter most easily when matter is approximately the same size as the photon wavelength.
All radiation with wavelength longer than those of x-radiation interacts primarily as a wave phenomenon.
X-rays interact with electons
Uv with molecules
VL cones and rods, living cells
Microwaves hamburger

20. Quantum Theory
“X-rays are created with the speed of light (c), and they exist with the velocity (c) or they do not exist at all” – Max Planck
German physicist
Receive a nobel prize in 1918 – whose mathematical and physical theories synthesized.
Rel. bet. F and e

21. Planck’s Quantum Equation
E = hf
Where:
E = photon energy
h = Planck’s constant
f = photon frequency

22. The Constant of Proportionality
Also known as Planck’s constant (h), has a numeric value of 4.15 x10-15 eVs or 6.63 x10-34 Js.

23. What is the frequency of a 70 keV x-ray?
Sample problem
What is the frequency of a 70 keV x-ray?
1.69 x1019 Hz.

24. Practice Problem
What is the energy of a 960 kHz electromagnetic wave?

25. Practice Problem
What is the frequency of a 86 keV x-ray?

26. Matter and Energy Law of conservation of matter
Law of conservation of energy

27. Theory of Relativity E = mc2 Where: E = energy in joules
m = mass in kg
c = velocity of light in m/s
1 Joule = 6.24 x1018 eV

28. Sample problem
What is the energy equivalence of an electron (mass = x10-31 kg), as measured in joules and electron volts?
x10-15 J
51.15 x104 eV

29. What is the mass equivalence of a 90 keV x-ray?
Practice Problem
What is the mass equivalence of a 90 keV x-ray?

30. What is the mass equivalence of a 340-nm photon of UV light?
Practice Problem
What is the mass equivalence of a 340-nm photon of UV light?