8.2 Geometrical Optics Flashcards
geometrical optics
describes the behaviour of light at the boundary of a medium
explains reflect and refraction and the application of mirrors and lenses
rectilinear propogation
the tendency light to travel in a straight line when travelling through a homogenous medium
reflection
the rebounding of incident light waves at the boundary of a medium
the light waves travel BACK through the first medium rather than absorving into the second medium
law of reflection
incident angle = reflected angle
both measured from the normal line (perp. to the boundary of the medium)
all angles in optics are measured from which reference line
the normal line (perpendicular to the medium boundary)
NOT from the surface of the medium
what type of images to plane mirrors form
virtual images
plane mirrors
flat reflective surface
virtual images
form BEHIND the mirror
image appears to be the same distance behind the mirror as the object is in front of the mirror
real image
form on the same side of the mirror as the actual object
always inverted
2 varieties of spherical mirrors
concave
convex
center of curvature
the center of the spherically shaped mirror IF it extended into a complete sphere
radius of curvature
the distance between the center of curvature and the mirror
concave mirror
the center of curvature is located in front of the mirror
convex mirror
The center of curvature is located behind the mirror
concave mirrors cause parallel incident light rays to:
converge
convex mirrors cause parallel incident light rays to:
diverge
focal point (F)
the point at which all parallel beams are “focussed” after reflection in the mirror
focal length (f)
the distance between the focal point (F) and the mirror
magnification (m)
a dimensionless value that is the ration of the image distance to the object distance
also gives the ratio of the size of the image to the size of the object
if m < 0
the image is inverted (upside down)
if m > 0
the image is upright
if |m| < 1
the image is reduced
if |m| > 1
the image is enlarged
if |m| = 1
the image is the same size as the object
optics equation
magnification equation
refraction
the bending of light as it passes from one medium to another and changes speeds
index of refraction for a given medium (equation)
snell’s law
critical angle
when the refracted angle equals 90 degrees
the refracted light ray passes along the interface between the 2 media and never escapes the medium
how to calculate the critical angle
use snells law and let the second angle = 90
sin (90) = 1
total internal reflection
a phenomenon in which all the light incident on a boundary is reflected back into the original material
Results when the incident angle is greater than the critical angle
lenses vs mirrors
lenses REFRACT light
mirrors REFLECT light
lenses have two surfaces that affect light path
First surface: the surface when light enters from the air into the glass lens/object
Second surface: the surface where light exits the glass lens back into the air
converging lens
thicker at the center
used to see things up close
diverging lens
thinner at the center
used to see things far away
lensmaker’s equation
f = focal length
n = index of refraction of the lens material
R1 = radius of curvature of the first lens surface
R2 = radius of curvature of the second lens surface
lens power (equation)
hyperopia
farsightedness
unable to see things close to the eye
myopia
nearsightedness
unable to see things far away
multiple lens systems: lenses in contact
A series of lenses with negligible distances between them behave as a single lens
multiple lens systems: lenses not in contact
The image of one lens becomes the object of another lens
the image of the LAST lens is considered the “image of the system”
magnification for a system of lenses not in contact (equation)
spherical aberration
an optical problem that occurs when all incoming light rays end up focusing at different points after passing through a spherical surface
results in an image with blurry edges
speed if light in a VACUUM…
is constant for all wavelengths
in mediums other than a vacuum…
different wavelengths travel at different speeds
dispersion
when various wavelengths of light separate from each other
what CHANGES when a wavelength enters a medium with a difference index of refraction?
the WAVELENGTH changes
what DOES NOT CHANGE when a wavelength enters a medium with a difference index of refraction?
the FREQUENCY stays the same
chromatic aberration
the failure of a spherical lens to focus all colors to the same point due to dispersion
