Physics gr10 PT2

LOST (Location, Orientation, Size, Type)

• Location: closer than, farther than, or the same distance as the object to the mirror
• Orientation: upright (facing same up-down direction as object), or inverted (opposite)
• Size: same size, larger than, or smaller than object
• Type: real (“in front” of mirror), or virtual image (“behind” mirror)

Concave Mirrors

• A mirror whose reflecting surface curves inward
• Centre of curvature (C): all normals (90°) meet at this point (center of the circle, radius)
• Principal axis: the line that passes through the center of curvature (C) and is normal to the center of the mirror
• Vertex (V): the point at which the principal axis cuts the center of the mirror
• Focal point (F): the point on the principal axis through which reflected rays pass when the incident rays are parallel to and near the principal axis
• Radius of curvature: the distance from C (center) to the mirror at V (vertex)
• Focal Length: the distance between V (vertex) and F (focal point)

Concave Mirror Rules

• Two light rays from the tip of an object are needed to locate its image
• The point where the two reflected rays intersect will be the location of the image
• The base of the object will always be on the principal axis

Convex Mirrors

• A mirror that is curved outward
• Image appears where the extended reflected rays intersect behind the mirror
• Image for a convex mirror is always: closer, upright, smaller, and virtual

Refraction

• Light travels in straight lines, but bends when it passes from one medium to another
• Refraction occurs when the speed of light changes in different mediums
• Particles in a medium slow down the passage of light waves
• The more that light slows down, the more the light is refracted
• Refraction only occurs when light is entering or leaving a medium

Refraction Rules

• The part of the light beam that hits the medium first will slow down first
• Angle of refraction: the angle between the refracted ray and the normal
• When moving from low to high refractive index, light bends towards the normal
• When moving from high to low refractive index, light bends away from the normal

Dispersion

• Different amounts of refraction for each color
• A single beam of white light can be split into a rainbow of colors
• Dispersion: the refraction of white light into separate wavelengths (colors)

Index of Refraction

• The amount by which a transparent medium decreases the speed of light