Lighting 2 quiz 1 - fundamentals

What is light

Visually evaluated radiant energy

What is the cornea

The clear, outer parabolic portion of the ee. The curvature of the cornea provides most of the eye’s focusing power

What is the aqueous humor

Clear, watery fluid located between the cornea and the lens (posterior chamber). It is responsible for maintaining intraocular pressure in the eye. Nourishes the lens and the cornea

What is the iris

The outer colored portion of the eye that opens or closes depending ding on the amount of light trying to enter the eye

What is the pupil

The hole formed by an opening in the iris. The pupil changes size depending on the light level to allow more or less light into the eye. The pupil acts as the aperture of the eye.

What is the lens

Sits beyond the pupil and is responsible for secondary focusing of light entering the eye. It is flexible and has variable focusing power. Its purpose is to focus a clear image onto the retina

What are the ciliary muscles

A ring of muscles that are responsible for flexing and changing the shape of the lens (trampoline analogy). The adjustment of the lens via the ciliary muscles is called accommodation.

What is the vitreous humor

A thick clear gelatinous material that fills the space between the lens and the retina. It is about 80 percent of the eye by volume.

What is the sclera

The white, protective outer membrane of the eye.

What are the vitreous humor and the sclera responsible for in the eye

Maintaining the shape of the eye.

What is the retina

The light-sensitive layers of the nerve tissue at the back of they eye that receive images and sends them as electric signals through the optic nerve to the brain.

What does the retina contain

Three types of light-sensitive photoreceptors (a neuron that is directly sensitive to light), called rods, cones, and ipRGC’s

What are the rods and cones responsible for

image formation

What is the fovea

A small portion of the retina where light is focused. It contains a high density of cones and no rods

What are the extra ocular muscles responsible for

Smooth pursuit, saccades, and convergence

What is smooth pursuit

coordinated movement of eyes used to continuously follow a moving object

What is saccades

eyes quickly jumping from point to point when looking around not focused on a particular object

What is convergence

eyes tilting inward or outward to focus on one particular point

Characteristics of rods

120 million, only in periphery, active in low light levels, inactive in high light levels, one type, responsible for night vision (scrodtopic vision)

Characteristics of cones

6 million, located throughout retina, most dense in the fovea, responds to bright light, three types (long, medium, short), responsible for daytime color vision (phconetopic vision)

What is blind spot

carries signal from the retina to the brain. it is the reason for the blind spot

What are the retinal cells

photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells

What does irPGC stand for

intrinsically photosensitive retinal ganglion cells

What is photopic vision

daytime vision, color vision, cones fully engaged, rods fully disengaged

What is scotopic vision

nighttime vision, no color vision, cones fully disengaged, rods fully engaged

What is mesopic vision

vision in between, cones partially engaged, rods partially engaged

What is the optic nerve

bundle of nerve fibers that carries visual information from the eye to the brain

What is the wavelength of peak sensitivity of human photopic visual system according to V(lambda)

555 nm

what is the efficacy of monochromatic lights at peak sensitivity of human photopic visual system (555 nm) is

683 lm/watt

What is the wavelength of peak sensitivity of human scotopic visual system according to V(lambda)

507 nm

what is the efficacy of monochromatic light at peak sensitivity of human scotopic visual system (507 nm) is

1700 lm/watt

What visual defect is caused by unequal carving of one or more reflective surfaces in cornea

astigmatism

What is the Purkinje shift

the tendency for the peak luminance sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels

What is presbyopia

with age, the lens of they eye becomes less flexible and therefore less able to focus light on the retina

What happens to the eye with increasing age

lens yellows, lens hardens, lens thickens, pupils become smaller and less responsive to luminous change, color vision declines (decreased sensitivity of cells), cataracts form (clouding of the lens), are-related macular degeneration (fovea resides inside of the macula)

How does nearsightedness form

They eye is too long, the light rays focus in front of the retina

How does farsightedness form

the eye is too short. the light rays focus behind the retina

What is keratoconus

a thinning of the cornea causing a cone-shaped bulge to form

What is glaucoma

an eye condition that damages the optic nerve. this can lead to vision loss or blindness

How does color blindness form

marked by deficiency in one or more of the cone photoreceptors

What is monochromic color blindness

lacking at least two or possibly three of the cone photoreceptors. sufferers perceive the world in black and white

What is dichromacy color blindness

lacking one of the cone photoreceptors and color is reduced to two dimensions

What is protanopia in color blindness

complete absence of the long wavelength photoreceptors

What us deuteranopia in color blindness

complete absence of the medium wavelength photoreceptors

What is tritanopia in color blindness

complete absence of the short wavelength photoreceptor

What does the fovea contain a lot of

cones

What is V(lambda)

A standardized visual efficiency function. It is a standard observer that was determined as an average across multiple subjects and different experimental protocols. It represents an average observer under specific conditions. Accurate and reproducible quantifications of light source.

What are limitations of V(lambda)

Field of view (2-3 degrees), field luminance (less than 10 cd/m²), additivity assumption (lab phenomena), experimental methods (flicker photometry)

What is photopic luminous flux

Time rate of flow of radiant energy evaluated in terms of a standardized visual response. (phi, lumen [lm])

What is the equation of luminous flux

phi = 683 integral from 780 nm to 380 nm [P(lamda)*V(lambda) d lambda]

How is luminous flux measured

integrating sphere. luminous flux typically includes all light emitted by a luminaire

What is luminous intensity

The luminous flux per unit solid angle in the direction in question (I, candela [cd])

What is the formula for luminous intensity

I = phi/omega → I = phi/steradian → I = phi/4(pi)

What is a steradian

A solid angle subtended by a surface area whose area is equal to the radius of the sphere

How is luminous intensity measured

Using a goniophotometer. Typically uses a stationary detector. Provides measurements at all angles by a revolving mirror or by rotating the light source.

What is illuminance

The areal density of the luminous flux incident at a point on a surface (E, lux or footcandle)

What is the formula for illuminance

E = phi/A → E = I/D² → E = (I*cos(theta i))/D²

What is the inverse square law

The illuminance E at a point on a surface varies directly with the intensity I of a point source, and inversely as the square of the distance D between the source and the point
E = I/D²

What is the inverse square cosine law

A law stating that the illuminance on any surface varies as the cosine of the angle of incidence. The angle of incidence is the angle between the normal to the surface and the direction of the incident light.
E = (I * cos(theta i)) / D²

How is illuminance measured

With an illuminance meter

What is exitance

The areal density of luminous flux leaving a surface at a point (M, lumens/area)

What is the equation of exitance

M = E * rho (reflectance)

How is reflectance measured

rho = flux(on) / flux(off)

How is transmittance measured

tau = flux(thru) / flux(on)

What is specular reflection

The angle between the reflected ray and normal to the surface will be equal

What is diffuse reflection

Optical radiation is reflected at many angles

What is an example of a specular surface

Mirror, chromium, stainless steel

What is an example of a diffuse surface

White paint, limestone, white paper

What is an example of a spread surface

Porcelain enamel, processed aluminum

What is spread reflection

Reflection that exhibit no directional control except for a specularly reflected ray with an intensity of approximately 5-15% of the incident light

What is a lambertian surface

Perfectly diffuse, and equally bright in all directions. Has equal luminance from all viewing angles

Describe, reflectance, transmittance, and absorptance

The ratio of the reflected flux to the incident flux; the ratio of the transmitted flux to the incident flux; the ratio of the absorbed flux to the incident flux

What is the cosine law

I(theta) = I(normal)*cos(theta)

What is the equation relating reflectance, transmittance, and absorptance of a surface

rho + tau + alpha = 1

What is luminance

Spatial flux density emitted by a surface in a particular direction (L, cd/m²)

T/F: We only see light that is emitted or reflected from a surface

T

What is the formula for luminance

L = Iv / Ap = I / A*cos(theta)
L = I(normal) / A
Iv = I(normal)*cos(theta)

L = Iv / Ap = I(normal)*cos(theta) / A*cos(theta) = I(normal) / A

For a lambertian surface, how can luminance be found

L = I(normal) / pi

How is luminance measured

Luminance meter