P3.2 - Light + Lenses Flashcards
Reflection, Refraction, Diffraction + Lenses
the reflected image and object ko characteristics [3]
-same size
-same distance from mirror
-laterally inverted
refraction
change in direction of a light ray passing form one medium to another / bending of light as it travels from 1 medium to another
refractive index
ratio of the speeds of a wave in 2 different regions
formula for refractive index (sin)
sin i / sin r
critical angle
angle of incidence at which the angle of refraction is 90 degrees and above which all light is totally internally reflected
total internal reflection
when angle of incidence in denser medium is larger than the critical angle and the ray gets completely internally reflected (it follows all the laws of reflection)
4 characterstics of a formed image (due to lens)
-enlarged / same size / smaller
-diminished and upright / inverted
-virtual and real
-where (in relation to F and 2F)
principle axis
line passing through the center of the lens and perpendicular to the axis of the lens
principal focus (focal point / focus) (F)
point where parallel rays coming from distant object get converged / focused (meet) after they pass through the lens
focal length
distance from the center of the lens to the principle focus (F)
formula for sin critical angle
1 / refractive index
real image
created by rays in a diagram actually meeting (on the other side of the lens from where object is) and so can be projected onto a screen
virtual image
created by imaginary rays in a diagram meeting and so can’t be projected onto a screen (rays diverge so they meet behind object and image is magnified and formed behind object)
what happens when rays in a ray diagram are parallel?
they meet at infinity
Snell’s Law
when light is refracted, angle of incidence and angle of refraction (sins) are always in proportion
formula for refractive index (speed of light)
speed of light in vacuum (3 x 10^8) / speed of light in medium
how fast does light travel in a denser medium?
slower
what happens to the bending of light and speed of light if the refractive index is high?
bending effect is greater, light slows down
what is dispersion of light
refraction of white light (to ROYGBIV) by a glass prism
what colour has the highest frequency
violet
what colour has the longest wavelength
red
when ray leaves, its parallel to what? (refraction)
incident ray
formula for speed (frequency and wavelength)
speed = frequency x wavelength
diffraction
bending around (scattering) of waves as they pass through a narrow gap or obstacle when wavelength is comparible (matching) to the gap
when is diffraction effect the maximum?
when the gap is comparible to the wavelength (same size)
wavefront
imaginary line drawn perpendicular to the crest / trough
optical density
how much a material is able to slow down light
does frequency change when medium changes?
no
what happens to ray when going from rarer –> denser (speed + direction)
slower + bends / refracts towards the normal
what happens to ray when going from denser –> rarer (speed + direction)
faster + bends / refracts away from normal
reflection
wave bouncing off a plane surface (wall / mirror / interface between 2 substances)
where does the incident ray, reflected ray, and normal all lie?
same plane
what happens to light on a rough surface?
scattering of light wave (light goes in all direction)
plane surface
flat at the point at which the wave interacts with the material
what causes refraction of light?
density
what is wavelength (wavefront)
distance between 2 wavefronts
when a ray leaves from denser –> medium, which way does the ray bend?
away from the normal
