P3 - waves (reflection, refraction, diffraction, critical, total internal reflection, light drawing, lens) Flashcards
define refraction
-change in direction of wave as they pass through different mediums
define reflection
-wave bounces off a plane surface at the same angle it came from
define diffraction
-bending at the ends of a wave as it passes through a narrow gap
define plane surface
2D flat surface
define normal
perpendicular line from the surface
does the wave speed, frequency and wavelength change in reflection
no for all
rays in reflection
-incident
-reflected
rays in refraction in order
-incident
-refracted
is there a normal in refraction and reflection
yes
does the wave speed, frequency and wavelength change in refraction
- f is constant
-v & λ changes
what happens when incident ray is 0 (at normal) for reflection & refraction
-no reflection/ refraction happens
does the wave speed, frequency and wavelength change in diffraction
no change to all
how does size of wave length affect how wave is diffracted
-short wave length, less diffraction
virtual lines in reflection
-distance from obj to mirror is same as distance from virtual image to mirror
-virtual image lines are dotted
-the reflected ray and dotted lines meet
change in v & λ from deep to shallow water
-deep - shallow = v & λ decrease
-f is constant
properties of light
-form of radiation
-travels in straight lines
-transfers energy
-travels as waves
-travels through vacuum
-3 x 10^8 m/s
define luminous & eg
-produce light
-sun, lamp, torch
define non- luminous & eg
-reflect light
-moon, pen, book …
diff of light in white & black
-white reflects all colours
-black absorbs all colours
experiment to know light travels in a straight line
-light through a hole in a dark room
-if light not travel in straight lines = room would be lit
define monochromatic light
-light of a single λ & 1 colour
why are some colours visible
-the colour is reflected while the other colours are absorbed
refraction from less dense medium to more dense medium ( n )
-LDTN
-decrease speed - towards normal
refraction from more dense medium from less dense medium ( n )
-MDAN
-increase speed - away from normal
how to show a surface is a mirror
-hatched lines behind the line
-all rays behind mirror are virtual
define critical angle
-when the refracted ray is perpendicular to normal
-varies with medium
define total internal reflection
-when incident angle is greater than critical angle, there is not refraction - only reflection
-in transparent medium
- has to be from more n to less n & incident angle is more than C
how is diffraction affected by size of gap
bigger gap = decreased diffraction
why do radio waves diffract more than light waves
they have longer wavelengths
what happens when incident angle is more than critical angle
-total internal reflection
-no refraction - only reflection
v from light blue medium - dark blue medium
-slow down
law of reflection
- incident angle = reflected angle
- rays & normal lie on the same plane
Snell’s law
n = sin ( i angle ) / sin( r angle )
3 formulas to find refractive index
- n = sin ( i angle ) / sin ( r angle )
- n = 1/ sin ( C )
- n = c / speed of light in medium
( use sin^-1 if needed to convert to angle)
note: C = critical angle, c = 3 x 10^8 m/s (speed of light in vacuum )
what happens if a barrier is put at the end of a ripple tank
- waves are reflected
- change in wave front
what happens if a transparent barrier is put in ripple tank
-waves are reflected or refracted
what happens if a barrier with a gap is put in a ripple tank
-waves are diffracted
how does gap size affect diffraction
-f is constant
-small gap = arc
-big gap = unchanged with edge bent
define virtual image
image that cannot be captured on a screen
-laterally inverted
-upright
-virtual
define real image
image than can be captured on a screen
define image
copy of a real object
types of lenes
-convex - converging lens - rays come to 1 particular point
-concave - diverging lens - rays scatter
how is the focal length & principle focus diff in converging & diverging lens
converging - principle focus & focal length after lens
diverging - principle focus & focal length before lens - lines to principle focus are dotted
note: refractive index is constant
types of reflection & their causes
-regular reflection - plain surface
-diffuse reflection (scattered rays) - uneven surface
characteristics of plain mirror
-upright
-virtual
-laterally inverted
-same size as object
stages in endoscopy
-light passes through a bundle optical fibers in patients stomach
-reflected light passes through second bundles of optical fibers
-inside of stomach reflect light
-optical fibers take light to eye piece
-doctor can see through eye pieces
what happens when 2 mirrors are perpendicular to each other
- a laterally inverted C shape
-all angles are same size
note: your right is the same as the right in the mirror
how to find distance of object to image
distance from image to mirror x 2
note: only convex lens produce real images
word, symbol & units for magnification formula
-image distance from optic center/ obj distance from optic center
-no units & symbols
types of magnification
- ( + ) - image is larger than obj
- ( - )- image is smaller than obj
examples of magnification
-magnifying glass
-microscope
requirement for magnification
obj must be closer to lens than principle focus
word, symbol & units for power of lens formula
- 1/ focal length
- P = 1/ f
P = m^-1
f = m
-positive for convex lens
-negative for concave lens
how is converging affected by focal length
shorter focal length, more converging
drawing for convex lens for image beyond focal point 1 (f1) - real image
-obj on left side
-ray 1 parallel to principle axis until lens and bends to f1
-ray 2 passes through optic center of lens and meets ray 1
drawing for convex lens for image before and at focal point 1 (f1) - virtual image
-obj on left side
-ray 1 parallel to principle axis until lens and bends to f1
-ray 2 passes through optic center of lens
-if obj > f, rays meet at obj side
-if obj = f, rays don’t meet - image is not formed
-properties of image at u>2f
-example
-image position
-real
-inverted
-diminished
-camera & eye
-image position: f<u<2f
-properties of image at u=2f
-example
-image position
-real
-inverted
-same size
-photocopier
-image position: 2f
-properties of image at f<u<2f
-example
-image position
-real
-inverted
-enlarged
-projector
-image position: >2f
-properties of image at u=f
-example
-image position
-virtual
-upright
-enlarged
-spotlight
-image position: infinity
-properties of image at u<f
-example
-image position
-virtual
-upright
-enlarged
-magnifying glass
-image position: same side as obj
-properties of image at u<f
-image position
-real
-inverted
-highly diminished
-image position:
note: refractive index cannot be less than 1
what refractive index do you use depending on medium
-L - M : n
-M - L: 1/n
-check is ans is sensible
what must angle r with angle i depending on medium
-L - M : r < i
-M - L: r > i
note: erect = upright
define principle axis
line perpendicular to lens which passes through the optic center
define focal point (principle focus)
point in principle axis where light rays are parallel to the principle axis coverage or appear to diverge from
define focal length
distance between optical center and principle focus
rules when drawing
1) ray parallel to principle axis & pass through principle focus
2) ray that passes focal point emerges parallel to optical axis on other side of lens
3) ray that passes through center of lens has no change
what type of lens is the eye
convex
how is a real image produced
by the actual intersection of rays projected on a screen
how is a virtual image produced
by the apparent intersection of rays that cannot projected on a screen
what type of image is formed by a plane mirror
virtual, image size is same as object
what comes with virtual & real images
virtual, upright, laterally inverted
real, inverted
