3. ELECTROMAGNETIC SPECTRUM
• Consist of 7 components
– Radio waves
– Microwaves
– Infra-red radiation
– Visible light
– Ultra-violet waves
– X-rays
– Gamma rays
105 m
10-14 m
Wavelength
Rich Men In Vegas Use X-ray Goggles
4.
5. PROPERTIES OF LIGHT
• Wavelength (λ)
• Energy of light (J) α 1
λ
• Power (W) – rate of flow of energy. (W or J/s)
6. • Irradiance – rate at which light energy is
delivered to a unit area is known as the
intensity of light or irradiance.
Irradiance = J/s/cm²
• Dose of light = it is the total amount of light
delivered to the skin & is equal to the product
of irradiance & time of exposure.
Dose = J/cm²
12. Application of Electromagnetic waves
Ultra-Violet (UV) Radiation (10-8 to 10-7)
• Sunlight is the main source of UV radiation
• Ultraviolet lamps are used in sunbeds for
artificial tanning.
• Used in hospital for sterilisation - kill bacteria
and viruses
13. Application of Electromagnetic waves
Visible Light (10-7)
• Only part of the EM spectrum that can be detected by
human eye.
• Wavelength: 400nm (violet) to 700nm(red)
• Laser can be used in industries
to weld metals together and in
medicine.
• Optical fibres in telecommunications
14. Application of Electromagnetic waves
Radio waves (10-1 to 105)
• Longest wavelengths
• Able to go around obstructions due to their
long wavelength
• Used in radio broadcasting,
telephone transmission, television,
radar, navigation system
15. Application of Electromagnetic waves
Microwaves (10-3 to 10-1)
• Microwave oven – cause the water molecules
in the food to vibrate. The vibration causes
friction at a molecular level which will heat up
the food.
• Satellite communication and television –
signals are transmitted through aerial dishes
to satellites in the space.
16. Application of Electromagnetic waves
Infra-red Radiation (10-7 to 10-3)
• All object emit infra-red radiation
• We experience infrared-radiation in the form of heat
• Ear thermometer: measure the amount of infra-red
radiation that emanates from the eardrum.
• Used in remote controls for electronic devices and
infra-red motion detectors.
17. Application of Electromagnetic waves
X-Rays (10-13 to 10-8)
• used to produce the X-ray images to examine
a person’s body or tooth decay
• used in X-ray scanners in airports
• can penetrate through all materials except
lead.
18. Application of Electromagnetic waves
Gamma Rays (10-14 to 10-10)
• It can be used to treat cancer by killing cancer
cells.
• Cause serious damages to living tissues.
28. Types of sun protection
• Systemic sun protection
- Beta – carotene
- Anti – malarial drugs
- Psoralens
29. Systemic sun protection
• BETA – CAROTENES
Mechanism of action
- Photo oxidised by UVR and this spares the cell
components from being photo damaged.
- Free radical scavenger & free radical quencher.
30. Beta carotene
• Uses
- Erythropoetic porphyria
- PLE
- SU
• Doses
- 30-120µgm in children
- 120-300µgm in adults
31. Antimalarials: Actions in Dermatology
• Bind to porphyrins and facilitate their
clearance in urine
• Solubilization and mobilization of hepatic
porphyrins and their clearance
• Ability to bind to melanin and antioxidant
activity: ?Role in photosensitive disorders
• Binds to melanin in retina leading to retinal
toxicity
32. Systemic sunscreen?
• Useful for diseases exacerbated by UVB (SCLE >
ACLE) as well as those exacerbated or induced by
UVA (polymorphous light eruption & its variants &
majority of photosensitivity dermatoses)
• Blocks effects of exposure on skin as well as other
organs esp. in LE
• Antioxidant effect & blockage of a cascade of
immunologic actions that follow light exposure
33. Anti - malarials
• Uses
- PLE
- SU
- PCT
- SLE & DLE
• Doses
- Chloroquine = 250-500mg/day
- Hydroxychloroquine = 200-400mg/day
34. Anti - malarials
• Monitoring
- Ophthalmic examination
- Visual acuity
- Perimetery
- Color vision
- Ophthalmoscopic avaluation
(at every 6 months interval)
37. Systemic sun protection
• Psoralenes
- 8 MOP
- TMP
(in conjunction with carefuly controlled exposure to either
sunlight (PUVAsol) or an artificial source of UVA (PUVA) can
be effective method of increasing skin’s resistance to the
damaging effect of UVB component sun light)