1. Light as a stimulus Flashcards
What is spectral power distribution
It refers to the mix of wavelengths emitted by a source of radiation. The energy in watts is emitted over a range of wavelengths
What is Wein’s displacement law?
Max wavelength is inversely proportional to absolute temperature in Kelvin.
Max wavelength = L (2.9 X 10^-3)/T (temp in K)
What is incandescence?
Objects that emit visible radiation when heated to high temperatures
What is luminous efficacy?
The efficiency with which a light source converts electrical energy into light. The ratio of input power (watts) vs the amount of light emitted
What is colour temperature?
The temperature in kelvin of a black body radiator with the same colour as the light source.
What are the two types of reflectance?
- Specular (smooth surface)
- Diffuse (Rough surface)
What is Vλ?
Human spectral luminosity function.
This equates the power of an energy source to it’s visibility.
The human eye’s spectral sensitivity to brightness.
What is Kλ?
Spectral luminous efficacy
The efficiency of light at various wavelengths in stimulating the human visual system
Define flux
The rate of flow of energy
What unit are solid angles measured?
Measured in steridian.
1 Steridian is equal to solid angle subtended by area r2 in sphere radius r.
What are the methods of obtaining Vλ ?
- Brightness matching - colours of similar wavelength compared for brightness
- Heterochromatic flicker photometry-
2 wavelength presented alternately at 25Hz. The minimum flicker point is defined as equal luminance.
How is Vλ used?
In colorimetry, it forms the central colour matching function in the CIE 1931 colour space. It’s the standard function used in CIE for lighting.
