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