Reflection

Def

• Light rays are always straight lines

• Normal ray is perpendicular to the mirror

• Incident ray is to inicial ray and reflected ray is the after

• Angle of incidence = angle of reflection (measured from normal

• Lies on the same plane

SALT (Size, Attitude, Location, Type)

• If it's more opaque, it is real, since light can not penetrate it

• According to the law of reflection, we find the reflected line and extend it over the mirror, and where they meet is the point.

• After reflection, it must pass through focal point

How to find reflection of an object in a concave mirror (3 rays):

• One ray is vertical to the object (may or may not pass F)

• Second ray passes focal point

• Third ray passes focal point

• After reflection is perpendicular to principal access (just draw line down from the PA to the intersection)

*If object is in between F and C, there will be an image (larger, upright, virtual)

• C is 2F the length from V on PA

*If object is on F, there will be no image

*If object is in front of F, it would be a virtual image (behind the mirror)

*If object is on C, there is an image (same, inverted, real)

*If object is behind C, there is an image (smaller, inverted, real)

How to find reflection of an object in a convex mirror:

• One ray is parallel to PA and will reflect along F (passes through F)

• Second ray has the same angle as the first, but on the other side of PA

• Third line is just a parallel line from point A’s reflection

*All images in convex is smaller than original as well as virtual, and it would usually only be the first two rays

*If object is in front of F, there is an image (smaller, upright, virtual)

*If object is between C and F, there is and image (smaller, upright, virtual)

• Refraction bends images

• Water - 1.33 (index of refraction)

Snell’s Law

• Air = optically less dense

• Water = optically more dense

*Whichever is denser, light travels through it slower

• The angle from the normal ray for a more dense object is smaller

Formulas:

R = 2F

• R is also referred to as “C”

Mirror Equation — 1/F = 1/Di + 1/Do

Magnification Equation — m = image height/object height = Hi/Ho = -Di/Do

Keywords:

Virtual — can’t be touched (considered a type)

• Use dotted line

• If screen is placed at the image position, no image will appear

Real — can be touched (considered a type)

• If you placed a screen at the image position, an image would appear on the screen

Magnification — larger same size smaller

Index of Refraction — defined by speed of light in a vacuum over the speed of light in that material

• Must be greater than 1

Position — ack

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Concave — curved inwards

Convex — curved outwards

PA (Principal Access)

F (Focal point)

R (Focal length)

• Positive for concave

• Negative for convex

V (Vertex) —

Center of Mirror —

Ho — height of object

Hi — height of image

• Positive or images upright

• Negative for images inverted

Do — distance from object to mirror

Di — distance from reflection to mirror

• Positives for object in front mirror

• Negative for object behind mirror