Physics Ch.14 Refraction
Terms in this set (70)
the bending of light as it travels from one medium to another (the bending of a wave front as the wave front passes between 2 substances in which the speed of the wave differs)
if light travels from one transparent medium to another at any angle other than staight on (normal to the surface)...
the light ray changes direction when it meets the boundary
angle of refraction (θr)
the angle btwn the refracted ray & the normal
angle of incidence
refraction occurs when...
when light's velocity changes
when light moves from a material in which its speed is higher to a material in which its speed is lower (ex: air->glass)...
then the ray is bent toward the normal
if the ray moves from a material in which its speed is lower to one in which its speed is higher...
then the ray is bent away from the normal
if the incident ray of light is parallel to the normal...
then no refraction(bending) occurs
refraction can be explained in terms of...
the wave model of light
the direction of propagation of the wave is perpendicular to the wave front & is what we call...
the light ray
the frequency of the light _________ change when the light passes from one medium to another
index of refraction
the ratio of the speed of light in a vacuum to the speed of light in a given transparent medium
index of refraction formula
index of refraction=speed of light in a vacuum/speed of light in medium
the larger the index of refraction is, the slower light travels in tht substance & ...
the more a light ray will bend when it passes from a vacuum into that material
use the value n=1.00 for air when solving problems
due to refraction objects appear to be...
in different positions
light is bent toward the normal when it travels from a ...
a medium with a lower index of refraction (air) to one w a higher index of refraction (water)
an underwater object seen from the air above appears...
larger than its actual size bc the image, which is the same size as the object, is closer to the observer
what affects the index of refraction?
wavelength; the amt that light bends when entering a diff. medium depends on the wavelength&speed of the light
why is a visible spectrum produced when white light passes through a prism?
each color of light has a diff. wavelength (ROYGBIV) therefore each color of the spectrum is refracted by a diff. amt (dispersion)
snell's law determines...
the angle of refraction for light traveling btwn any 2 media
the greater the index fraction...
the more refraction occurs
snells law formula
(index of refraction of first medium x sine of the angle of incidence = index of refraction of second medium x sine of the angle of refraction)
curved surfaces change...
the direction of light bc the direction of the normal line differs for each spot on the surface of the medium, so when light passes through the medium, the change in the direction of the light rays varies from pt to pt.
a transparent object that refracts light rays such that they converge or diverge to create an image
-form images by refraction
-images can be either real or virtual depending on type of lens&placement of the object
formed when rays of light actually intersect to form the image & they can be projected onto a screen
form at a pt from which light rays appear to come but do not actually come & can NOT be projected on a screen
lens thicker at middle than at the rim *refer to pic
lens thinner at middle than at rim *refer to pic
focal length (f)
the image distance for an infinite object distance (distance from focal pt to center of lens)
every lens has a focal pt on each side of the lens bc...
the light can pass through the lens from either side *refer to pic
converging lenses&diverging lenses both have...
2 focal pts & only 1 focal length
*refer to pic
ray diagrams of thin-lens systems help identify...
(also possible to calculate these values;thinlense equation&magnification formula)
lenses for which the thickness of the lense is small compared to the radius of curvature of the lens or the distance of the object from the lens
rules for drawing referrals rays
characteristics of converging lenses
can produce real or virtual images of real objects *pic
characteristics of diverging lenses
-ALWAYS produce virtual images from real objects
-image is upright
-magnification is always less than 1 (image size is reduced) *pic
-equation that relates object&image distances for a lens(applies when lens thickness<focal length)
-can be applied to converging & diverging lenses if u adhere to a set of sign conventions*picture/table
1/p + 1/q = 1/f
(1/distance from object to lens) + (1/distance from image to lens) = (1/focal length)
real image in back of lense =
positive image distance
virtual image in front of lens =
negative image distance
converging lense (aka positive lenses) =
positive focal length
diverging lense (aka negative lenses) =
negative focal length
magnification (M) by a lens depends on...
object & image distances
Magnification of a lens formula
M = h'/h = -q/p
(magnification=image height/object height=distance from image to lens/distance from object to lens)
when magnitude of the magnification of an object is <1 ...
the image is smaller than the object
when magnitude of magnification is >1 ...
image is larger than the object
(-) for M indicates...
image is real&inverted
(+) M indicates...
image is upright & virtual
the transparent front of the eye, called the ______, acts like a lens, directing light rays toward the light-sensitive ______ in the back of eye
small lens in eye tht refracts light
-when the eye attempts to produce a focused image of a nearby object but the image position is behind the retina, making distant objects clear but near objects blurred
-causes: eye too short or ciliary muscle cannot adjust properly to focus image
-can be fixed by converging lens
-occurs when eye is longer than normal or when max focal length of lens is insufficient to produce a clear image on retina
-distant objects NOT seen clearly bc the distant object is focused in front of the retina
-can be corrected by diverging lens
when using a combination of lenses, the image formed by the first lens is treated as the...
object for the second lens & the image of 2nd lens is final image of system
*if image formed by 1st lens is in back of the 2nd lens thn image is virtual so p is (-)
2 ex.s of the use of 2 converging lenses?
1) compound microscopes (used for greater M, creating real,inverted, enlarged image
2) refracting telescopes (1st lense creates real,inverted image & 2nd creates magnified,virtual)
causes of total internal reflection
when light moves along a path from a medium w higher index of refraction to one w a lower index of refraction
def. of total internal reflection
the complete reflection that takes place w/in a substance when the angle of incidence of light striking the surface boundary is>the critical angle
The angle of incidence at which refracted light makes an angle of 90° with the normal
when angle of incidence(Øi)=the critical angle(Øc), then...
the angle of refraction(Ør) = 90°
critical angle formula
sin Øc=Nr/Ni , for Ni>Nr
sine(critical angle)=index of refraction of second medium/index of refraction of first medium ONLY if index of refraction of 1st medium > index of refraction of second medium
*remeber 1/sin is really
a phenomenon of nature produced by refraction (bending of light rays)in the atm. when there are large temperatures differences btwn the ground & air
The process of separating polychromatic light into its component wavelengths
imp property of index of refraction
index of refraction decreases as...
how are rainbows created
-by dispersion of light in water droplets
1)ray of sunlight strikes droplet in atm
2)thn its refracted at the front of the surface of the drop
3)violet light refracts the most & red light the least
4)thn back at surface of drop the light is reflected&returns to front of surface where it undergoes refraction again as it moves from water to air
results from focal pts of light rays far from principal axis of a spherical lens are diff. from the focal pts of rays w the same wavelength passing near the axis
arises from the wavelength dependence of refraction & it is the focusing of diff. colors of light at diff. distances behind a lens & it can be reduced by a combination of converging & diverging lenses made by 2 diff. types of glass
chromatic aberration for a diverging lense is ________ to that for a converging lens
decrease in speed of light in material(v) to ...
increase index of refraction (n) & c is constant(speed of light in vacuum)