optics unit test
Properties of light
light is an electromagnetic wave that transfers light energy through radiation, without a medium. It is produced from luminous sources
incandescense
materials like metals reach high temperatures and begin to glow
electric discharge
when an electrical current passes through a gas and produces light
phosphorescence
phosphors absorb ultraviolet light at high energy and release visible light slowly over time
fluorescence
when an object absorbs ultraviolet light and releases it immediately
chemiluminescence
light produced by a chemical reaction
bioluminescence
chemiluminescence occuring in a living thing
triboluminescence
when certain types of crystals are scraped or banged together, they produce sparks
LED
light emitting diodes allow current to flow slowly instead of fast with the use of semiconductors, and they last more time
Electromagnetic spectrum
classification of waves by their energy levels. Smaller levels of radiation mean larger waves. Radio, Infared, visible light, ultraviolet, x-rays, gamma rays
everyday uses for electromagnetic waves
Radio waves: Used to listen to the radio, tv, etc
Infared waves: Infared cameras
Ultraviolet waves: used in forensics to see fingerprints, etc
X-rays: Used in hospitals for x rays
Gamma rays: used to treat cancer patients in radiation therapy
Laws of reflection in a plane mirror
1. the angle of incidence is the same as the angle of reflection
2. the incident ray, reflected ray, and normal all lie in the same plane
specular reflection
reflection off of a smooth, shiny surface
diffuse reflection
reflection off of an irregular or dull surface
uses for plane mirrors
seeing ur own reflection, periscopes, and solar cookers
SALT plane mirror
Same size, upright, behind mirror, virtual
virtual vs real image
Virtual image: an image formed by light coming from an apparent light source, and is formed by rays that aren't from the location of the image
real: an image that can be seen on a screen as a result of light rays arriving at the screen location
convex vs concave mirrors
Convex mirrors have a reflection that comes from the outer surface of the reflection, and light rays diverge
concave mirrors come from the inner surface of the reflection, and light rays converge at one point
convex mirror examples
car mirrors, security mirrors in a parking garage etc
concave mirror examples
dentist mirror, telescope, makeup mirrors
SALT convex mirrors
smaller, upright, behind mirror, virtual
SALT concave (beyond c)
smaller, inverted, between c and f, real
SALT concave (at c)
same size, inverted, at c, real
SALT concave (between c and f)
larger, inverted, beyond c, real
SALT concave (at f)
no image
SALT concave (between f and mirror)
Larger, upright, behind mirror, virtual
Magnification equations
M = image height/object height
M = image distance/object distance
Index of refraction equations
speed of light: 3.00 x 10^8 m/s
n = c (speed of light in vaccum)/v (speed of light in the medium)
n = sin(angle of incidence)/sin(angle of refraction)
refraction
when light travels from one medium to another, it bends, this is known as refraction
rules of refraction
1. the incident ray, refracted ray, and normal are on the same plane
2. the incident ray is in the first medium, and the refracted ray is in the second medium, the normal separates the two
bending rules
1. if the speed of light is slower in the second medium than the first, it will bend towards the normal
2. if the speed of light is faster in the second medium, it will bend away from the normal
partial reflection
some light may reflect off the surfave of the second medium as it travels from one medium to another
total internal reflection
total internal reflection is when light completely reflects off of the inside wall of a denser medium, and doesnt pass into the less dense medium
when does total internal reflection happen
1. light is travelling more slowly in the first medium than the second
2. the angle of incidence is large enough so that no refraction occurs in the second medium
3. the angle of incidence is larger than the critical angle (the angle of incidence at which the angle of refraction is 90 degrees)
applications of total internal reflection
fibre optic cables, and diamonds
apparent depth
objects in water appear to be closer rhan they are, because light refracts when it reaches the water, and our brain perceives the light as coming in a straight line from the fish
mirage
an image of light from the sky is produced as light refracts through air of different densities. Total internal reflection occurs when light reaches the hottest air layer, and lifht hets reflected back to cooler air layers, and refracted and creating an image of sky on the ground
rainbow
light refracts when it enters a raindrop, which separates the light into visible colours
converging lenses
refracts parallel rays so that they all pass througha single point on the other side of the lense
diverging lense
refracts parallel rays so that they diverge on the other side of the lens