G10 Reflection of Light Flashcards
Light ordinarily travels in straight line path called ray.
In order to represent light, rays are used.
Rays are lines with an arrow head at its end.
The arrow head tells the direction where the light ray is going.
imaginary line perpendicular to the surface
Normal line
is the angle which an incident ray makes with normal line
The angle of incidence (𝜃i)
is the angle which the reflected ray makes with the normal
The angle of reflection (𝜃r)
The angle of incidence and the angle of reflection is always measured from the normal line
The idea that the path which light travels is the one that uses the shortest time is called _.
This means that in order for light to go from one point to another, it takes the shortest and most efficient path available to it.
Fermat’s Principle of Least Time
states that the incident and reflected rays lie in the same plane with the normal and that the angle of reflection equals the angle of incidence, 𝜃i = 𝜃r
law of reflection
Types of Reflection
Diffuse Reflection
Specular Reflection
happens when light is reflected into multiple directions.
This is true when light hits a rough surface.
Objects that might appear smooth to touch but still performs _ _ are actually microscopically rough. eg. eggshell
Diffuse reflection
happens when light is reflected at only one path.
This is true when light hits a smooth surface.
Microscopically smooth surface are good reflectors of light. e.g. mirrors
Specular reflection
is a smooth, flat reflecting surface.
It creates images that are located on the same distance as the object from the mirror and with the same height but are inverted from left to right.
plane mirror
An imaginary line passing through the center of the sphere at the exact center of the mirror.
Principal Axis
The point on the mirror’s surface where the principal axis meets the mirror
Vertex
The point in the center of the sphere from which the mirror was sliced
Curvature (C)
Halfway between the center of curvature and vertex
Focal point (F)
The distance between the vertex and the focal point
Focal length (f)
is a curved mirror wherein the reflecting surface is bulging towards the viewer.
This mirror focuses light away from the focal point that is why it is called diverging mirror.
convex mirror
In order to find where an image will be located if an object is placed in front of a mirror, a technique called _ _ is used.
Different rays are used to represent the light rays coming from the object.
ray diagramming
a reference ray starting from the object going parallel to principal axis is drawn. It reflects through the focal point, F, after it hits the mirror
principal ray
second reference ray goes through F and then goes parallel to principal axis after hitting the mirror
focal ray
third reference ray goes through C then goes back along itself through C
central ray
Since the F and C of a convex mirror are situated behind the mirror’s surface, dotted lines are extended along the reflected rays to points behind the mirror. The intersection of two or more rays locates the image.
location
orientation
size
type
Location is at the back the mirror
Orientation is upright
Size is smaller (or diminished)
Type is virtual
It is possible to mathematically calculate where an image will show up if distance of the object is known. It is also possible to know the radius of curvature of a mirror given the location of object and the image.
p – object’s distance from the mirror
q – image’s distance from the mirror
f – focal length
mirror equation
1/p + 1/q = 1/f
Units for distances and focal length should be consistent.
The magnification of an image can be computed either by using the height of the image and the object or their distances. A positive M means that image is upright and virtual and a negative value means it is inverted and real.
M=h’/h or q/p
is a curved mirror wherein the reflecting surface is on the inner surface of the sphere so that the center of the mirror sinks away from the viewer
concave mirror
First ray: From the object parallel to the principal axis and will be reflected to the focal point.
Second ray: From the object through the focal point and is reflected parallel to the principal axis.
Third ray: From the object through the central point and will be reflected back to the central point.
The point where the rays intersect is where the image will appear.
