Notes on Light and Optical Systems Review notes
Definition of light: Electromagnetic waves that lend themselves to the sense of sight. (Modern definition)
Pythagorus – Light comes from our eyes. BUT if light came from our eyes, we would see in the dark. This does not happen.
Euclid – Light travels in straight lines and reflects. This gave us The Ray Model of Light
THE RAY MODEL OF LIGHT
(smart notebook)
Refraction and Reflection
Reflection: Light hits a surface and then is sent back.
Law of Reflection:Normal
Surface
X YX=Y - Always
Incident rayReflected ray
Refraction: Light bending when it passes through a new medium (water, air, space, oil …)
Air – More dense
Light Diverges
Space – Less dense
Myopia & Hypermetropia
Myopia: Near-sightedness. The focal point meets in front of your retina. A diverging lens corrects.
Hypermetropia: Far-sightedness. The focal point meets behind your retina. A converging lens corrects.
Astigmatism: Skewed hypermetropia or myopia, but not solely one of the two. Needs a very specific oblong lens to fix.
The Eye:
Pupil: Receives incoming light.
Iris: Controls the amount of light.
Lens: Focus the light.
Cornea: protect the eyeball.
Retina: Forms the image.
Ciliary Muscles: To contract the lens to focus light differently.
Optic Nerve: The nerve that connects the eye to the brain to make sense of what you are seeing. It introduces a blind spot where the nerve attaches to the retina.
3 types of material for light
Transparent: Completely see-through. Allows all light to pass through.
Translucent: Mostly see-through. Allows some light to pass through, the rest gets reflected
Opaque: Blocks light. Cannot see through.
Characteristics of Light:
Light is a form of energy
Light travels in straight lines
Light reflects off of material
Light is equally intense in all directions from a light source
Light is an electromagnetic wave
Light changes speed when it enters a new medium (i.e. water to air)
5 types of light
Incandescence heat causes a filament of metal to glow (i.e. a regular light bulb)
Fluorescence ultraviolet light is absorbed by fabric particles, which in turn emit some of the energy as light (i.e. fluorescent lights)
Phosphorescence light is stored and released later as visible light (i.e. glow in the dark paint)
Chemiluminescence light is released by a chemical reaction (i.e. glow sticks)
Bioluminescence light produced by living organisms (i.e. fireflies)
Aperture -> Pupil
Lens -> Lens
Diaphragm -> Iris
Film -> Retina
3 primary colours of light
Q: How do we see colour? A: The Retina
Rods: Help us see contrast (white -> grey -> black)
Cones: Help us see colour