properties of light and reflection Flashcards
medium
the substance through which light travels (air, water)
ray
a straight line with an arrowhead that shows the direction in which light waves are travelling
ray tracing
using rays to predict the location, size, and shape of the image of an opaque object
2 parts of fermat’s principle
light follows the shortest straight line between two points
when light reflects into the same medium from which it originated, its speed will remain constant
reflection
change in direction of a light ray when it bounces off a surface
incident ray
a ray of light that travels from a light source toward a surface
angle of incidence
the angle between the incident ray and the normal
normal
a line that is perpendicular to a surface where a ray of light meets the surface
reflected ray
a ray that begins at a point where the incident ray and the normal meet
angle of reflection
the angle between the reflected ray and the normal
3 laws of reflection
incident ray, normal, and reflected ray lie on the same surface
angle reflection (r) = angle of incidence (i)
reflected ray and incident ray are on opposite sides of the normal
how to draw ray diagrams: step 1
draw the _____ using a ruler
incident
how to draw ray diagrams: step 2
at the contact point where the incident ray hits the surface, draw a ______ by measuring a __ degree angle with a protractor
normal / 90
how to draw ray diagrams: step 3
measure the longest ________ between the incident ray and the _____. make a mark to indicate the same angle on the other side of the normal. this is the ____________
angle of incident (i) / normal / angle of reflection
how to draw ray diagrams: step 4
draw the _________ from the contact point through the mark using a ruler
reflected ray
how to draw ray diagrams: step 5
what 5 things do you label?
incident ray reflected ray angle of incidence (i) angle of reflection (r) normal
why do we see objects in mirrors?
light rays are reflected off the objects and back to your eye
plane mirror
a mirror with a flat, reflective surface
step 1 of reflections:
when a light shines on the object, it reflects off all the points on the object in _________.
all directions
step 2 of reflections:
the rays reach the mirror, follow the ___________, and reflect toward your eye.
laws of reflection
step 2 of reflections:
even though the rays are reflected, your brain assumes light rays travel in a straight line, and treats them as if ____________
they had come form a point behind the mirror
how do we find out where the eye “sees” the image?
extend the reflected rays until they meet at a point behind the mirror
what kind of image forms? (L.O.S.T.)
location
orientation
size
type of image
location (L.O.S.T.)
image distance (distance between mirror and image) = object distance (distance between mirror and object) image distance can be the same as, farther than, or closer than the object distance
orientation (L.O.S.T.)
upright, inverted, or reversed
size (L.O.S.T.)
image size = object size
size can be the same size, larger than, or smaller than the object
type of image (L.O.S.T.)
virtual image (forms behind mirror) or real (forms in front of mirror)
step one of ray diagram
incident ray from top of object horizontally to mirror surface, reflects back, extends behind mirror
step two of ray diagram
repeat 1, except from other points on object
step three of ray diagram
reflected ray from image to eye from all points
step four of ray diagram
draw normal where reflected rays (see 3) meets mirror surface
step five of ray diagram
draw incident ray from top of object to mirror (at normals)
step six of ray diagram
measure incident and reflected ray angles
what are the characteristics of images in plane mirrors?
same size, same distance, same orientation; virtual image
lateral inversion
the apparent reversal of the mirror image’s left and right when compared with the object
