How we See Light, Laws of Reflection, Plane and Curved Mirrors

How do we see light

We only see light that travels into our eye brain, dont see light that doesnt enter our eyes

Ray Diagram and Light Ray

Ray diagrams show how light moves from object to eye

Light Rays are lines that show direction and path light travels

light can be…

absorbed, reflected or refracted

How we see colour

Colour depends on wavelengths reflected

• black absorbs all

• white reflects all

• blue absorbs only blue and reflects rest

Transparent VS Translucent VS Opaque

Transparent - Light passes through easily, see through

Translucent - Some light passes through, some reflected/absorbed, appears foggy

Opaque - No light passes through, can’t see through

Plane Mirrors are

flat mirrors

Image VS Mirror VS Reflection

Image - Reproduction of object produced through use of light

Mirror - Any polished surface that exhibits reflection

Reflection - Bouncing back of light from any surface

Incident Ray VS Reflected Ray VS Normal

Incident Ray = Incoming ray that strikes surface

Reflected Ray = Ray that bounces off reflective surface

Normal = Imaginary line perpendicular to reflecting mirror surface, placed where incident ray hits mirror

Angle of Incidence VS Angle of reflection

Incidence Angle = Angle btwn incident ray and normal

Reflection Angle = Angle btwn reflected ray and normal

Laws of Reflection in Plane Mirrors

1. Angle of Incidence = Angle of Reflection

2. Incident Ray, Reflected Ray and Normal all lie in same plane

Specular VS Diffuse Reflection

Specular - Light reflects off smooth surface, in same ddirection

Diffuse - Light reflects off rough dull surface, in scattered and different directions

Image VS Virtual Image

Image - Reproduction of Object through use of light

Virtual Image - Image formed by light that does not come from image location, but appears to come from image

SALT

Size, Attitude, Location, Type

SALT: Plane Mirror

Same size, Upright (but appears backward), Behind mirror (same distance from it as object), Virtual Image

Curved Mirror

Mirror with single curvature. Concave (Converging) faces towards object, Convex (Diverging) faces away from object

What’s C, F, V, Principal Axis

C - Centre of Curvature where surface used to make mirror

F - Focus, midpoint btwn C and V

V - Vertex, where principal axis meets mirror

Principal Axis - Line through C and mirrors midpoint

Characteristic Rays of Concave

Parallel to surface reflects through focus

Passing through focus reflects parallel

Passing through C reflects back through it

Striking vertex reflects at same angle

SALT: Beyond C for Concave

Smaller, Inverted, Btwn C and F, Real

SALT: At C for Concave

Same size, Inverted, At C, Real

SALT: Btwn F and C

Larger, Inverted, Beyond C, Real

SALT: At F

No Image

SALT: Inside F

Larger, Upright, Behind mirror, Virtual

Convex Mirrors

curve outward from object

Characteristic Rays for Convex

Parrallel to Principal Axis reflects along line that intersects focus behind mirror

Ray going through on path to focus reflects off mirror parallel to principal axis

Ray going through on path to C reflects back through same line

Striking vertex reflects at same angle on opp side of principal axis

SALT: Convex Mirrors

Smaller, Upright, Behind Mirror, Virtual

Found by extending reflected ray as dotted line behind mirror