Vision Flashcards
What is the sclera?
Thick white outer covering of the eyeball that’s attached to 6 muscles
What’s the cornea?
Front part of sclera, covers up iris and pupil. It’s coloured and transparent
What’s iris
Colours r brown, blue, green, and grey. Ring of muscle that contracts and relaxes automatically to regulate amount of light entering eye.
What r ciliary muscles?
Hold lens in place, attached to lens by ligaments
What’s retina
Layer of light sensitive cells at back of eye and has many blood vessels and nerves
What r rods
Are 120 million in 1 eye. Colours r black, white, and shades of grey. Sensitive to levels of light (detect dim light)
What r cones
Are 6 million in 1 eye. Sensitive to colour (detects bright light)
What is optic nerve
Sends nerve signals to brain
What’s blind spot
Area of retina where optic nerve and blood vessels connect. No rods or corns
What’s normal vision?
6/6 meters, or How clear or sharp vision normally is at 6 meters. In NV, cornea and lens reflect light to produce clear image in retina. Image is upside down and reversed
What r refractive vision problems?
When eye can’t properly focus on image in retina
What’s myopia
Nearsightedness. Can c nearby things clearly but not distant objects. 1/3 of population has it. Focal point of an eye with myopia is in front of retina.
What’s hyperopia
Farsightedness. Eye can c distant objects clearly but has trouble focusing on close-up objects. 1/4 of population. Focal point of eye with this is behind the retina
How does lens change when u focus on distant object?
Light doesn’t bend much, ciliary muscles relax and lens is normal shape
How does lens change when u focus on nearby object
Light rays enter at angle, refract and change direction and ciliary muscles contract
How does astigmatism affect eye?
Cornea has irregular curvature, so visions blurred
How does presbyopia affect eye
Eye can’t focus on nearby or faraway objects due to age
How do u correct myopia?
Concave lens in front of eye spreads incoming light
How do u correct hyperopia?
Convex lens used to slightly refract light before it enters eye
What happens during laser surgery?
Fine bean of light’s used to reshape the cornea to adjust focal point
Define refract
To make a ray of light Change direction when it enters at angle
What’s light
Form of energy that can be detected by human eye. It travels from source directly to your eyes, some bounce off objects and travels to eye
Explain sources of light
Light energy comes from natural and artificial sources. Sun’s most important natural source of light.
What’s luminous
Objects that emit (give off) energy in form of light (sun, candle). In luminous objects, input energy transforms into light energy. Things that r very hot become luminous at height temperature and begin to emit light
What’s nonluminous
Doesn’t emit light, only reflects light from other sources (moon, books, etc)
What’s incandescence
Process of emitting light energy because of high temperature. These light sources have Large amounts of input energy because of thermal energy, therefore these light sources aren’t efficient
What’s thermal energy
Thermal energy can heat metal to high temperature, and emits light (from dull red to yellow to white to blue-white as object gets hotter and hotter)
What’s phosphorescence
Process of emitting light from short time after receiving energy from another source, (e.g. Light switches that glow in the dark)
What’s electric discharge
Process of emitting light because of electricity passing through a gas (lightning)
What’s fluorescence
Process of emitting light while receiving energy from another source (fluorescence tubes used in schools). Fluorescence tubes use electric discharge and phosphorescence
What’s chemiluminescence
Process of changing chemical energy into light energy with little or no change in temperature (glow sticks)
What’s bioluminescence
Some living things can make themselves luminous using a chemical reaction similar to chemiluminescence (fire flies, fish)
What’s shadow
An area where light has been blocked by a solid object
What’s umbra
Dark part of shadow, some light from the source reaches here
What’s penumbra
Lighter part of shadow, some light from source comes here
What’s transparency
Measure of how much light can pass through a material
What’s transparent material
Particles let light pass through readily (plastic wrap)
What’s translucent material
Particles transmit light but also reflect some so a clear image can’t be seen through material (frosted glass, candle)
What’s opaque material
Particles don’t allow any light to pass through. All light energy is reflected or absorbed (stone, brick)
Describe absorbing and reflecting light
Light strikes an opaque material, no light’s transmitted. Some of the light energy is absorbed by material and is converted into thermal energy, and some rays of light bounce off the object to be reflected
What describes the amount of light energy that’s absorbed it reflected?
Colour/sheen (shininess). Black and dark coloured materials absorb more light energy than white and light coloured materials
What’s a visible spectrum?
Bond of colour u can c in a rainbow. 6 main colours r red, orange, yellow, green, blue, and violet- called spectral colours
What’s white light
Spectral colours, red to violet. Different spectral colours are reflected and absorbed depending on characteristics of the object. This is why we c object in specific colours (if blue lights reflected off object, we c blue). If all parts of visible spectrum r reflected, we c the objects as white. If none’s reflected, we c black
What’s electromagnetic spectrum
Entire range of radiant energies other than light r (UV) ultraviolet radiation, x-ray, and microwaves
What’s wave
Vibration that transfers energy from 1 location to another. The vibration’s a regular repeated motion that produces regular wave patterns. Wave can be created by stretching out length of rope (or springs) and vibrating 1 end back and forth. Light behaves in a way similar to mechanic waves. Reflects off surfaces or changes directions when passing through different materials
What’s wavelength
Distance between 2 adjacent crests or 2 adjacent troughs
What’s crest
Farthest point above resting position
What’s trough
Farthest point below resting position
What’s amplitude
Maximum distance above or below resting position
What’s frequency
Vibration of number of cycles In a period of time. It’s indicated in hertz (h2) or cycles per sec. for waves, a cycle’s a complete wavelength. Energy of different parts of the electromagnetic spectrum depend on wavelength, and high frequencyC has high energy
