AP Physics Chp 25

Wavefronts – location of the same point for the same phase of the wave

Rays – perpendicular to the wavefront

Plane waves – all rays are parallel

Reflection

Specular vs Diffuse

Law of Reflection

θi = θr

Plane Mirrors (flat)

ImageUprightSame SizeBehind the mirror (virtual)

• How big does a wall mirror really have to be to be “full length”?

• Spherical Mirrors

• Concave vs Convex

• Principal Axis – line through the C, center of curvature

• Focal length f = ½ R concave f = - ½ R convex

• If the rays are close to the axis then they are called paraxial rays

• Spherical aberration

• Parabolic mirrors – all rays that are parallel to axis reflect through the focal point

• Ray diagrams

• 1 – tip of object to mirror and then through f• 2 – tip of object through f then parallel to axis• 3 – tip through C (1 line)

• Intersection is the image location

Sign conventions f, d + is in front of the mirror - is behind the mirrorSometimes using multiple mirrors can cause the

object distance to be - h + is upright - is inverted

Mirror Equation

1 1 1

o id d f

Magnification EquationA negative m means it’s inverted

i i

o o

h dm

h d

• If an object is located 3 m in front of a concave mirror that has a radius of 1 m, where is the image and what is it’s magnification?

1 1 1

o id d f

1 1 1

3 0.5im d m

i i

o o

h dm

h d 0.6

0.23

mm

m