1. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 2 Electromagnetic Radiation, Magnetism, and Electrostatics Essentials of Radiologic Science

2. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins ELECTROMAGNETIC RADIATION All types of electromagnetic radiation are a form of energy Consists of simultaneous electric and magnetic waves 90 degrees to each other

3. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins ELECTROMAGNETIC RADIATION

4. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins PARTS OF A WAVE Wavelength (λ) Amplitude Cycle

5. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins PARTS OF A WAVE Frequency (f) –Unit: Hertz (Hz) Period Velocity (v)

6. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins PARTS OF A WAVE

7. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins THE ELECTROMAGNETIC SPECTRUM The full range of all of the different types of electromagnetic radiations arranged in order of increasing energy: –Radio –Radar/microwaves –Infrared –Visible light –Ultraviolet –X-rays and gamma rays

8. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins THE ELECTROMAGNETIC SPECTRUM

9. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins ELECTROMAGNETIC RADIATION CHARACTERISTICS Travel at c, the speed of light –3 × 10 8 m/s Travel as photons or quanta

10. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins RELATIONSHIP BETWEEN f, λ, v, AND E As frequency (f) increases, energy (E) increases –Demonstrated by the formula: E = hf (h = Planck’s constant: 4.15 × 10 -15 eV-s) As frequency (f) increases, wavelength (λ) decreases –Demonstrated by the formula: c = fλ

11. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins THE INVERSE SQUARE LAW The intensity of the radiation decreases with an increase of distance from the source (and vice versa) Intensity is inversely proportional to the square of the distance Formula: I 2 = I 1 (d 1 /d 2 ) 2 I 1 = Old intensity I 2 = New intensity d 1 = Old distance d 2 = New distance Formula may also be expressed as: I 1 /I 2 = d 1 2 /d 2 2

12. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins THE INVERSE SQUARE LAW

13. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins MAGNETISM Definition: Ability of a lodestone or magnetic material to attract iron, nickel, and cobalt Types of materials: –Ferromagnetic –Paramagnetic –Diamagnetic –Nonmagnetic

14. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins MAGNETISM Magnetic domain: A group of atoms aligned in the same direction; exhibits a magnetic field A magnetic field surrounds a magnet or moving electric current Units: gauss (G) and tesla (T) –1 tesla = 10,000 gauss

15. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins THE LAWS OF MAGNETISM Every magnet has a north and south pole Like poles repel; opposites attract Inverse Square Law

16. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins LIKE POLES REPEL; OPPOSITES ATTRACT

17. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins ELECTRIFICATION Definition: Process of charging an object by adding or subtracting electrons Three methods: –Friction –Contact –Induction

18. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins LAWS OF ELECTROSTATICS Repulsion-Attraction Coulomb’s Law Distribution Concentration Movement

19. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins LIKE CHARGES REPEL; UNLIKE CHARGES ATTRACT