Electromagnetic Radiation

EMR

Light that travels in transverse waves, caused by the acceleration of electrons. Needs changing electric and magnetic fields

Maxwell

Determined that changing electric fields will produce a perpendicular magnetic field and EMR

Michelson

Used an 8-sided rotating mirror to observe the speed of light

EMR Properties

Travels in a straight line, uniform motion

Specular Reflection

Parallel incident rays reflect as parallel incident rays

Diffuse Reflection

Parallel incident rays reflect irregularly and in different directions

Law of Reflection

The angle of incidence is equal to the angle of reflection

Normal Line

A line perpindicular to the surface at the point of reflection

The angle of incidence and reflection is measured from the normal line

Images in a Mirror

Light rays are reflected from the object and are reflected into our eyes

They appear to be coming from behind the mirror

Image Characteristics

Real or Virtual

Inverted or Erect

Enlarged or Diminished

Vertex

The centre of the curved mirror

Centre of Curvature

Double the focal length

Focal point

Half the distance to the centre of curvature

Focal Length

The distance from the mirror to the focal point

Concave Mirror

Converging mirror, light rays converge on the focal point

Convex Mirror

Diverging Mirror, light rays appear to converge on the focal point

Mirror Ray Diagram Rules

First ray is parallel to the principle axis and then goes through the focal point

Second ray goes through the focal point and then parallel to the principle axis

Refraction

The bending of light as it travels from one medium to another

Snell’s Law of Refraction (More Dense)

Light bends towards the normal

Wavelengths get shorter

Speed gets slower

Index of refraction is larger

Snell’s Law of Refraction (Less Dense)

Light bends away from the normal

Wavelength increases

Speed increases

Index of refraction decreases

Total Internal Reflection

When the angle of incidence is greater than the critical angle this results in total internal reflection

Critical Angle

The angle of incidence that results in an angle of refraction that is 90 degrees

Dispersion of Light

Light splits into its color components when passed through a prism

Red disperes the leasts, Blue disperses the most

Concave Lens

Diverging Lens, thinner in the middle

Convex lens

Converging Lens, thicker in the middle

Lens Ray Diagram rules

First ray goes parallel to the principle axis then through the focal poitn

Second ray goes through the optical centre

Huygens Principle

A wave front is made up of an infinite number of points that each act as the source of a new wave. The line that is tangent to the circles is the wave front

Diffraction

The change in shape and direction of light or a wave as it passes though an opening or around an object.

Poisson Spot

When incident light rays on a round object diffract to produce a bright spot in the centre of the shadow

Young’s Experiment

Used to determine the wave nature of light

Color and Diffraction

The longer the wavelength the more it diffracts

Red diffracts the most, Violet Diffracts the least

Polorization

Unpolarized light vibrates in all directions.

Polorized light vibrates in one direction.

Only transverse waves can be polarized