Nature of Light

Light Light can be modeled as a wave and a

particle

Transverse, electromagnetic wave

Photons — particles of light

Speed of Light Vacuum — 3.00 x 108 m/s

Water — 2.25 x 108 m/s

Glass — 1.97 x 108 m/s

Generally decreases as medium increases in density.

Intensity

Intensity is referred to as brightness.

Intensity decreases as distance from the origin increases. Why? Photons spread out over wider area.

Lasers

A device that controls the way energized atoms release photons.

The word originates from the phrase light amplification by stimulated emission of radiation.

Properties of Lasers

Monochromatic — one specific color

Coherent — organized; moves in step with others

Directional — tight beam; strong and concentrated

Modeling With Rays

Rough surfaces reflect at all angles. This is called diffuse reflection.

Smooth surfaces reflect light rays in one direction. This is called specular reflection.

Modeling with Light Rays

The angle at which the ray strikes the surface is called the angle of incidence.

The angle at which the light is reflected is called the angle of reflection.

Law of Reflection

The angle of incidence is equal to the angle of reflection.

Both are measured from a line perpendicular to the surface called the normal.

Mirrors

As light reflects off a mirror, some rays hit your eye and your brain interprets this as an image behind the mirror.

Flat Mirrors

Show a virtual image, located behind the mirror at the same distance as the object is from the surface.

Ex: Bathroom Mirror

Concave Mirrors

Used to focus reflected light (magnification)

Can create a real image in front of the mirror.

Ex: reflecting telescopes

Convex Mirrors

Used to gather more images.

Ex: Mirror in corner of store or on side of car (“objects in the mirror are closer than they appear”). Let you see around a corner.