optics

grade10 academic science optics review

Light

Form of energy that travels in straight lines

Electromagnetic spectrum

Range of all light waves (radio to gamma)

Visible light

Portion of the spectrum humans can see

Reflection

Bouncing of light off a surface

Incident ray

Incoming light ray

Reflected ray

Bounced light ray

Normal line

Perpendicular line to surface

Law of reflection 1

Angle of incidence equals angle of reflection

Law of reflection 2

Incident ray, reflected ray, and normal lie in the same plane

Regular reflection

Smooth surface produces clear image

Diffuse reflection

Rough surface scatters light

Plane mirror

Flat mirror

Convex mirror

Diverging mirror that spreads light

Concave mirror

Converging mirror that focuses light

Vertex (V)

Centre point of mirror

Principal axis

Straight line through centre of mirror

Principal focus (F)

Point where rays meet or appear to meet

Focal length

Distance from vertex to focus

Centre of curvature (C)

Point at twice the focal length

Image

What is seen in a mirror or lens

Object

Actual source of light

Real image

Can be projected on a screen

Virtual image

Cannot be projected on a screen

SALT

Method to describe images: size, attitude, location, type

Refraction

Bending of light when it moves between media

Medium

Material light travels through

Angle of incidence

Angle between incoming ray and normal

Angle of refraction

Angle between refracted ray and normal

Index of refraction (n

Measure of how much light slows in a material

More refractive medium

Material where light moves slower (higher n)

Air to water

Light bends toward the normal

Water to air

Light bends away from the normal

Dispersion

Splitting of white light into colours

Critical angle

Angle of incidence where refracted ray is 90 degrees

Total internal reflection

Light reflects instead of refracting

Conditions for TIR

Occurs when light goes from higher to lower refractive index and exceeds critical angle

Lens

Transparent object that bends light

Converging lens (convex)

Brings light rays together

Diverging lens (concave)

Spreads light rays apart

Optical centre (O)

Middle of lens where light passes straight through

Principal axis (lens

Straight line through centre of lens

Principal focus (F)

Point where rays meet or appear to meet

Focal length (lens)

Distance from optical centre to focus

Ray rule 1 (converging lens)

Parallel ray passes through focus

Ray rule 2 (converging lens)

Ray through optical centre goes straight

Ray rule 3 (converging lens)

Ray through focus exits parallel

Converging lens image

Can be real or virtual depending on position

Diverging lens image

Always virtual

Myopia

Nearsightedness corrected with diverging lens

Hyperopia

Farsightedness corrected with converging lens

Camera

Uses converging lens to focus image

Human eye

Lens focuses light onto retina

Mirage

Refraction in hot air creates illusion of water

Twinkling stars

Refraction through moving air layers

Sunset refraction

Bending of light makes sun visible after it sets