Lecture 3 Part 2 Flashcards
List the blue light delivery options
Integrated within incubators
Free standing
Placement on the incubator
Blankets - bili blankets
What is blue light? And what is the blue light wavelength used for jaundice management?
It is a specific visible wavelength on the electromagnetic spectrum
450-490nm
What does irradiance mean?
Defined as power per unit area on a surface, given in W/m2
When is irradiance maximised? Explain
When the surface is perpendicular to the beam
The power of the light source and angle at which the light hits is important
The irradiance is maximised when the light is directly received by the surface
E (degree sign) = E x cos(degree sign)
Increasing the angle decreases the irradiance
Is it possible to deliver a uniform irradiance to a patient?
No, it’s usually more in the centre and the most as it is focused and then it disperses out
Explain the make up of a fluorescent lamp for blue light delivery
Sealed glass tube, inside which is a little mercury and an inert gas (usually argon) under low pressure
Inside surface of glass is coated with phosphor powder
An electrode at either end of the tube with a high potential difference
how does a fluorescent lamp actually work? Explain
When current is applied, electrons flow from negative to positive electrode
This energy changes the liquid mercury to a gaseous form
As the electrons collide with the gaseous mercury atoms, energy is transferred to the electrons of the mercury atoms, moving them to a higher energy shell
The electrons drop down to their previous level, losing energy as they do so in the form of UV light photons
For fluorescent lamps, explain exactly what happens in the energy shells for them to produce the UV light
Electrons orbit in distinct energy shells: 2, 8, 8
The closer the energy shell is to the nucleus, the tighter it is bound to the electron
The free electrons interact with the outer shell electrons of the gaseous mercury atoms
Electrons are given sufficient energy to promote higher energy orbit
Electrons instantaneously lose energy, returning to their former position and emitting light
The amount of light emitted is determined by the energy shell differences in mercury
Where is phosphor powder on the fluorescent lamp?
It is the coating on the inside of the glass tube
How does the phosphor powder impact the UV transmission from the fluorescent lamp? How does it create the visible light?
When the UV light strikes the coating, an outer energy shell of the powder is given energy, promoted to a higher energy shell and returns to its former position losing energy in the form of visible light
Light is emitted in all directions
What is the wavelength of visible light dependent on for the phosphor powder?
The energy difference between the orbital shells
How can visible light be tuned to the desired wavelength?
The right combination of phosphor materials result in this, so it can be made as desired to stay within the visible light range
What type of energy is lost as heat during visible light creation by the phosphor powder? And exactly is it?
Residual energy, this is the remaining energy that is left over in a system when a process has occurred
How is blue light produced? What is it made of?
LEDs
Semiconductor, which, under the right conditions, allows the flow of electron-hole pairs to produce visible light
Explain the process of LEDs
So you have p type and n type (positive and negative) in a semiconductor.
the p type is a side of excess holes (where electrons are missing which act like positively charged particles)
the n type is the side with an excess of electrons (negatively charged particles)
When a voltage is applied across the LED, the n type side moves towards the p type side and recombines with the holes
They release energy in the form of photons - light
The region where the electron-hole recombination occurs is called the depletion zone/junction, this is like an insulating layer
