3.01 - 3.03 Electro Mangnatic Spectrum.pptx

The electromagnetic spectrum refers to the entire range of electromagnetic radiation, which is energy that travels and spreads out as it goes, with different wavelengths and frequencies. It spans from long radio waves used in communication to the incredibly short gamma rays associated with nuclear reactions. Electromagnetic waves are created by the movement of electrically charged particles, and they travel through space at the speed of light. The study of the electromagnetic spectrum is crucial to understanding the fundamental nature of energy and light, with vast implications for technology, medicine, astronomy, and many other fields.

1. ELECTROMAGNETIC SPECTRUM

2. Introduction: Name of EMW and their wavelengths Nature of EMR: Wavelength, intensity, frequency, velocity. Physical Property : Reflection, absorption, penetration, Scattering. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 2 TOPICS

3. EMR is in form of a wave consisting of regular sinusoidal electric and magnetic field at right angle to one another. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 3 INTRODUCTION

4. EM SPECTRUM the range of electromagnetic waves placed in order of increasing frequency Includes 7 types of EM radiation 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 4

5. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 5 ELECTROMAGNETIC SPECTRUM

6.   Radio = Radio     Microwaves = Mikes     Infrared = In     Visible = Visible     Ultraviolet = Umbrellas     X-rays = X-box     Gamma Rays = Game   The radio was on while Mike played invisible umbrellas on his X-box game. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 6

7. Types of EM Radiation in Spectrum 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 7

8. 1. RADIO WAVES Longest wavelength Lowest frequency Uses: Radio broadcasting Satellite dish Television Cell phones 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 8

9. Radio Waves Lowest energy in EM spectrum 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 9

10. Are radio waves with very high frequency Uses: Cooking in microwave ovens Cell phones Radar images (Doppler) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 10 2. MICROWAVES

11. Radiowaves FM - frequency modulation AM - amplitude modulation Satellites 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 11 Types of EM Radiation Microwaves penetrate food and vibrate water & fat molecules to produce thermal energy

12. 3. INFRARED WAVES (IR) Felt as heat energy or warmth Given off by all warm objects Ex: Heat lamp Remote Controls Vegetation reflects short IR waves Radiators/heaters are long IR waves known as thermal IR or far IR 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 12

13. Infrared Radiation (IR) slightly lower energy than visible light can raise the thermal energy (heat) of objects thermogram - image made by detecting IR radiation 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 13 Types of EM Radiation

14. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 14 4. Visible Light Visible Light Only part on EM spectrum we can see ROY G. BIV - colors in order of increasing frequency R O Y G. B I V red orange yellow green blue indigo violet

15. White light is made up of all the colors in the rainbow (ROY G BIV) Prism - refracts white light and separates it into all the colors 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 15 4. VISIBLE LIGHT

16. Invisible sun light Produces Vitamin D Sunscreen protects our skin Sunglasses protects our eyes Can kill bacteria Insects can see UV light, we can’t 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 16 5. ULTRAVIOLET (UV)

17. slightly higher energy than visible light Types : UVA - tanning, wrinkles UVB - sunburn, cancer UVC - most harmful, sterilization 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 17 Ultraviolet Radiation (UV)

18. Ozone layer depletion = UV exposure! = more severe sunburns = cancer ! 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 18 Ultraviolet Radiation (UV)

19. 6. X-RAY 2 nd highest frequency (high energy) Used in airports and hospitals Given off by stars Can cause cancer 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 19

20. higher energy than UV can penetrate soft tissue, but not bones 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 20 X rays

21. Shortest wavelength Highest frequency (most energy) Nuclear explosions that occur within stars, like our sun Given off by stars and radioactive substances 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 21 7. GAMMA RAY

22. highest energy EM radiation emitted by radioactive atoms used to kill cancerous cells 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 22 Gamma rays Radiation treatment using radioactive cobalt-60.

23. R – RADIO WAVES – 0.1 mm to 100 km I – INFRA RED – 750 to 4000 nm V - VISIBLE LIGHT – 400 to 750 nm U – ULTRA VIOLET – 10 to 400 nm X – X-RAYS & GAMMA RAYS – 0.01 pm to 10 nm 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 23 INTRODUCTION

24. Velocity: 3 x 10 8 m/sec Velocity remains constant for all electromagnetic waves in vacuum. When wave will pass from a body tissue its velocity reduces markly. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 24 VELOCITY

25. Wavelength: it is a distance between a point on one electromagnetic wave and exactly same point on next wave. Frequency is inversely proportional to wavelength 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 25 WAVELENGTH B B’ A A’

26. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 26 FREQUENCY Frequency: number of complete waves passing any fixed point in one second. V = f * ʎ

27. Strength of electric and magnetic wave. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 27 WAVE AMPLITUDE

28. Wave energy depends on both wave intensity (Amplitude) and wave frequency. As the frequency is high more destructive nature of wave. Example : x-rays 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 28 WAVE ENERGY

29. Electromagnetic radiation interactions can occur: Penetration and transmission Reflection (No energy loss and so no effect on the material) Another possibility: 1. Absorption (Wave energy is absorbed and material will change nature or its composition & Properties) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 29 INTERACTION OF RADIATION WITH MATTER

30. In real situation all three happens together. The amount depends on wavelength or frequency of radiation & Nature and positioning of material. Eg. Light transmitted through window Another possibility is: Refraction Scattering (Reflection and refraction occurring in bulk of material) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 30

31. More atoms and molecules – slower the wave will travel. At junction of two kind of matter – wave thus have to change velocity. Wave will not change in frequency so wavelength will change. (v=f~) Eg: EMR wavelength is reduced when passing from air to glass as velocity is less in glass. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 31 REFLECTION AND TRANSMISSION OF RADIATION

32. If wave strikes a boundary and is slowed only part of wave energy is transmitted rest is turned back or reflected. When there is change in electrical medium of matter, reflection is inevitable. Amount of reflection depends on: Frequency of radiation Angle of incidence Nature of two medium 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 32

33. The direction of reflection depends on: Angle of incidence (Beam striking plane surface, AOI=AOR) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 33

34. The lens in the eyes refracts light, painting a picture of the outside world on the retina. The rods and cone cells of the retina fire off signals to the brain where the pattern of pulses is reconstructed to produce the mental image. The more the waves are reflected the less is penetration. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 34

35. This depends on angle of incidence. The greater AOI, greater wave energy reflected. If AOI=0, least energy reflected and greater amount of transmission. Eg: IR/UVR lamp should placed in such a way that rays strike at right angle. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 35

36. When radiation passes from one medium to another, it will be refracted unless the radiation is perpendicular. Eg : Glass-Air interface used in microscopes, lenses, cameras. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 36 REFRACTION

37. Refraction occurs when EMR are transmitted from one medium to another with an angle of incidence greater than zero. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 37 REFRACTION

38. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 38 REFRACTION

39. If a ray enters a medium in which it travels slowly, it bents towards normal. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 39

40. Absorption is reciprocal of penetration. For a homogeneous material the rate of absorption of wave energy is proportional to the energy present at that point. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 40 Absorption & Penetration

41. Penetration Depth – the depth at which 63% of the original radiation has been absorbed. Half value depth – the depth at which 50% has been absorbed. As depth increases absorption decreases. Different frequencies/wavelengths of radiation have different penetration depth in any particular material. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 41 Penetration Depth

42. Thus materials of a particular mature and thickness can be used as filters. Eg : Filtering Short UVR but leaving long UVR for some treatment. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 42

43. Filter is a medium which will absorb some EMR while allowing others to pass. Examples : window glass absorb UVR but allows to pass visible and IR X rays pass through the soft tissue but absorbs by bone. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 43 FILTERS

44. Radiation passing through non-homogeneous material may be partly scattered, reducing depth of penetration. In biological tissue, cells, tissues and fibres do not reflect the rays much, so much energy is transmitted and so less scattering. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 44 Scattering

45. Scattering: direction of radiation in material altered by numerous reflection or refraction. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 45 SCATTERING

46. Amount of scattering depends upon wavelength of radiation. Longer wavelength scatter less. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 46

47. Reflected Transmitted (penetrate) – with refraction or without refraction Scattering – In non homogenous material direction of radiation is altered by various reflection and refractions Absorption – energy of radiation is used or convert into other form 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 47 INTERACTION OF RADIATION WITH MATTER

48. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 48 INTERACTIONS OF RADIATION WITH MATTER

49. They ionize atom if their frequency are high enough. Example : LASER as ionizing radiation 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 49 IONIZING RADIATION +VE e - e - e - e -

50. Atoms have positive charged nucleus and electrons occupying fixed, discrete orbitals. Electrons occupying a particular orbital all have same energy. By giving an energy to an atom an electron can be kicked to a higher energy level, in doing so atoms absorbs precise amount of energy. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 50

51. When electrons drop from higher energy level to lower precise amount of energy, equal to difference is released. This is emitted in form of photon. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 51

52. When atoms are bombarded with high energy electromagnetic radiation ie high frequency photons, it is possible to knock electrons from their orbitals and completely separate them from their parent atom. Parent atom deficient in electrons is positively charged and is called as ion. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 52

53. Ionization means that an electron has been separated from its atom. Radiation that has this effect is called ionizing radiation. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 53

54. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 54

55. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 55

56. It is produced whenever electric charges are accelerated. Radio waves : produce with high frequency alternating current in wire Heat emits IR radiation Atoms & ions are made to collide in low pressure gas giving energy. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 56 PRODUCTION OF EMR

57. Cosine Law: Intensity of rays at a surface varies with the cosine of the angle between the incident ray and normal. Cosine of 90 = 0 (minimum) Cosine of 0 = 1 (maximum) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 57 Laws

58. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 58

59. “The intensity of rays from a point source varies inversely with the square of the distance from the source.” I α 1/d 2 I1 / I2 = (D1) 2 / (D2) 2 I1 = intensity of at D1 distance I2 = intensity of at D2 distance 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 59 Inverse Square law

60. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 60

61. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 61

62. Rays must be absorbed to produce an effect. Rays are absorbed at surface, disappears and produce characteristic effect on site of absorption. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 62 LAW OF GROWTHUS

63. Beer Lambert Law :- Degree of absorption depends on the wavelengths of radiation and nature of absorbing material Kirchhoff’s law : It states that the good radiators are good absorbers. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 63

64. Wien’s Law: It states that the wavelength of maximal emission is inversely proportional to absolute temperature of the source so that the hotter the source shorter is wavelength of emitted rays. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 64

65. Stefan – Boltzman Law It states that the output of Infra-red lamp will depend on the temperature of the element and its radiating area. 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 65

66. Clayton’s Electrotherapy: Theory and Practice - Forster & Palastanga (Ninth Edition) Electrotherapy Explained – John Low & Ann Reed (Third Edition) 3.01 - 3.03 ELECTROMAGNATIC SPECTRUM 66 REFERENCE BOOK