OP - How is Light Produced? - Week 1 Flashcards Preview

OD1 - Integrated Ophthalmic Sciences & Preclinical Optometry > OP - How is Light Produced? - Week 1 > Flashcards

Flashcards in OP - How is Light Produced? - Week 1 Deck (15)
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1
Q

At what temperature do objects begin to emit visible light?

A

1.5K

2
Q

Name the two categories of light production.

A

Incandescence

Luminescence

3
Q

Define colour temperature.

A

Temperature at which a black body at the corresponding temperature would emit that wavelength.

4
Q

Define black body. Why is it named so?

A

The ideal incandescent source is called a black body. It is called a black body because the ideal incandescent source must also be a perfect absorber. The perfect absorber must be black.

5
Q

Describe Wein’s displacement law.

A

Peak wavelength decreases with temperature.

6
Q

Describe Planck’s law.

A

Extended Wien’s law to short wavelengths and gave the shape of the intensity versus wavelength curve for different colour temperatures.

7
Q

Describe Stefan-Boltzmann’s law.

A

Total amount of radiation emitted varies as the fourth power of the temperature.
σT^4

8
Q

How do real sources of incandescence differ from black bodies?

A

They always emit less radiation than the black body at the same temperature, because real bodies are grey, not black.

9
Q

Define luminescence.

A

Production of light by non-thermal or non-incandescent means.

10
Q

Name 4 types of luminescence.

A

Fluorescence
Phosphorescence
Chemi-luminescence

11
Q

Define electro-luminescence. Name examples.

A
Luminescence caused by electrical 
activity.
Gas lamps
Gas lasers
Solid states, LEDs, diodes
12
Q

How does electro-luminescence work? Name 2 ways.

A

Ionised gas can reassemble releasing light.
Atoms struck by electrons can have their electrons move up a shell. When they return to ground state, they release light.

13
Q

How do LEDs work?

A

Has 2 parts, n-type and p-type.
n-type is negatively charged with a lot of electrons.
p-type is positive, and has few electrons.
When a voltage is applied, a current flow is induced, and electrons meeting the deficiency results in the release of light.

14
Q

Describe the reaction used by the firefly to produce bioluminescence.

A

luciferin + luciferase + ATP + oxygen = excited product + luciferase + light

15
Q

Describe the difference between fluorescence and luminescence.

A

Luminescence - generation of light via a chemical reaction.

Fluorescence - absoprtion of light at one wavelength, and re-emission at another

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