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ray optics
the study of light
How does light travel?
in a straight line
How can a ray change direction?
refractions + reflection
luminous
a source that emits light (ex: the sun)
illuminated
a source that reflects light (ex: the moon)
opaque
a material that does not allow any light to pass through; may reflect some light
transparent
a material that transmits light; may reflect some light
translucent
a material that filters light; may reflect some light
luminous flux (P)
rate light is emitted
lumens (lm)
unit of measurement of luminous flux
illuminance (E)
rate light strikes a surface
lux (lx)
lumens per square meter
inverse-square law
as square of the distance increases, the number of rays illuminating an area decreases
luminous intensity
the luminous flux that falls on the inside of a 1m radius sphere
candela (cd)
unit of measurement of luminous intensity
How can intensity be increased?
brighter light and/or decreased distance
diffraction
the bending of light around a barrier
white
appears when an object reflects all visible light
black
appears when an object absorbs all visible light
When does color arise?
when certain wavelengths are absorbed while others are reflected; the reflected wavelengths are the colors that we can see
refraction
when light passes from one medium to another with a different density, different colors, or bent at a different angle
polarization
a process that forces light into a single plane of oscillation; reduces intensity by 50%
Doppler effect
an increase or decrease in wavelength as the observer moves toward or away from an object emitting the wave
blue shift
a negative change in wavelength, frequency increases
red shift
a positive change in wavelength, frequency decreases
Law of Reflection
when a ray of light hits a perfectly smooth surface, it bounces off it at an equal angle to the one that came in
the normal
the line perpendicular to the surface (represented by a dotted line)
angle from the normal to the surface
90 degrees
specular reflection
light reflected from a smooth surface at a definite angle
light rays are reflected in a parallel
image is preserved
diffuse reflection
produced by rough surfaces that tend tp reflect light in all directions
more common than specular reflection
angle between the incident ray and the reflected ray
(angle between normal & ray of reflection/incidence) * 2
plane mirror
flat surface that produces a virtual image of the real object, requires at least 2 rays
How is an image created?
By rays of light that travel from the object to the mirror
Reflected rays diverge causing an image to form “behind” the mirror
virtual image
images of real objects produced by plane mirrors
formed when reflected rays do NOT meet
What happens to the size of the image when it is reflected in a plane mirror?
the dimensions stay the same as the real object
image position & height
are preserved in a reflection (same as real object)
type of image that convex mirrors form
virtual
speed of light & main scientists
Galileo, Ole Roemer, & Albert Michelson
electromagnetic spectrum
radio → microwave → infrared → visible (ROYGBIV) → ultraviolet → xray → gamma
center of curvature (c)
the radius of the geometric center of the sphere that it is a piece of
focal point
halfway to the center of curvature. Where incident rays that are parallel to the principal axis converge after reflecting.
focal length
position of the focal point with respect to the mirror along the principal axis. Positive value with concave mirror.
f = *r/*2
principle axis
a straight line perpendicular to the surface of the mirror that cuts it in half.
Note
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