Unit 2: Lights and Geometric Optics

We are able to see because of…

light entering our eyes.

Medium

Any physical substance through which energy can be transferred

Light does not…

require a medium to travel through.

Radiation

A method of energy transfer that does not require a medium

Light is an example of…

electro magnetic wave

Electromagnetic Wave

A wave that has both electric and magnetic parts, does not require a medium, travels at the speed of light

Examples of electromagnetic waves…

Radio waves, microwaves, infrared light, visible light, UV light, X-Rays, Gamma rays (Low to High)

Visible Spectrum

The continuous sequence of colours that make up white light

Sir Isaac Newton…

was the fist person to separate light into the visible spectrum

The order of colour is…

ROY G BIV

When we see an image in a mirror…

it appears behind the mirror

Virtual Image

An image that appears to be where there is no light forming the image

You can predict where a virtual image will appear because…

The distance from the object to the mirror is the exact same as the distance from the image to the mirror and the object-image line is perpendicular to the imagine surface

L (In LOST)

Location

O (In LOST)

Orientation

S (In LOST)

Size

T (In LOST)

Type of image

An image in a plane mirror is…

Behind the mirror (L), Upright but backwards (O), Same size (S), Virtual (T)

Luminous objects can be seen because they…

produce their own light.

Non-luminous objects can be seen because…

light bounces off of them and into our eyes.

Incandescence

The production of light as a result of high temperature

Electric Discharge

The process of producing light by passing an electric current through a gas

Different colours of neon lights are produced by different gases

Neon: Red, Helium: Gold, Argon: Pale Violet Blue, Krypton: Greyish Off-White

Phosphorescence

Occurs when the absorption of UV light results in the emission of visible light over an extended period of time

Fluorescence

The immediate emission of visible light as a result of the absorption of UV light

Fluorescent lights use both electric discharge and fluorescence to…

create light

When the electricity is turned on, the mercury atoms emit…

UV Light/ Visible Light

Since they contain mercury, fluorescent lights…

should not be disposed in household trash

Chemiluminescence

The direct production of light as the result of a chemical reaction with little or no heat produced

The luminal reaction is used to…

Detect blood at a crime scene

Bioluminescence

The production of light in organisms as a result of a chemical reaction with little or no heat produced

When a chemical called luciferin mixes with oxygen from air…

bioluminescence occurs.

Triboluminescence

The production of light from friction as a result of scratching, crushing, or rubbing certain crystals

Light from a Light-Emitting Diode (LED)

A result of an electric current flowing in semiconductors

Semiconductors

A material that allows an electric current to flow in only one direction

LASER

Light amplification by stimulated emission of radiation

If you shine a white light on a prism…

the light separates into the colours of the visible spectrum.

If you shine red laser light on a prism, all of the light remains…

red.

First law of reflection

The angle of incidence equals the angle of reflection

Second law of reflection

The incident ray, the reflected ray, and the normal all lie in the same plane

a

Incident ray

b

Reflected ray

Specular Reflection

Reflection of light off a smooth surface. Parallel ray of incidence will have parallel ray of reflection.

Diffuse Reflection

Reflection of light off an irregular or full surface. Parallel rays of incidence will not have parallel rays of reflection.

Plane Mirror

Flat mirror

Incident Ray

The incoming ray that strikes a surface

Reflected Ray

The day that bounces off a reflective surface

Normal

The perpendicular line to a mirror surface

Perpendicular

At right angles

Angle of Incidence

The angle between the INCIDENT ray and the NORMAL

Angle of Reflection

The angle between the REFLECTED ray and the NORMAL