P14 lenses (paper 2) Flashcards
what type of images are always formed from a concave lense
virtual
what are the two types of lense
- convex
- concave
what lense is the one which seperates light rays
concave
what are the two types of reflection
- diffuse
- specular
what is diffuse reflection
when light is reflected in all directions from rough surfaces
what is specular reflection
when light is refleccted in one direction off of a smooth surface
what should you do to find the prosition of an object with a mirror
- draw a ray from object & reflect
- draw another ray & reflect
- extrapolate both rays
- image is formed where line cross
what are the two types of images
- virtual
- real
what are the two sizes of images
- magnified
- diminished
what are the two ways of images
- upright
- inverted
what are the other names of a convex and concave lense
- converging
- diverging
what is the focal length
the distance from the center of a lens to the point where light rays parallel to the principal axis are focused.
where is the principal focus of a convex image
where the rays all meet after hitting the lens parallel to the axis
where is the principle focus of a concave image
where the rays hitting the lens parallel to the axis appear to all come from
what are the rules when refraction in a convex lense
- parallel ray goes straight then through focal point
- central ray goes straight through centre of lense
- image is formed where the lines cross (real or virtual)
what are the rules when refraction in a concave lense
- parallel ray goes forward to hit lense ~ extreoplate back
- centeral ray goes through focal point infront of lense
- image is forced where lines cross
how do you calculate magnification
magnification = image height / object height
what is the law of reflection
angle of incidence = angle of reflection
define a real image
An image formed by a lens that can be projected on a screen.
define a virtual image
An image, seen in a lens or a mirror, from which light rays appear to come after being refracted by a lens or reflected by a mirror.
describe refraction
Refraction is where light changes direction when it enters a new material.
why does refraction happen
becuase light rays change speed when entering a new material and bend either towards or away from the normal
when velocity of a light ray decreases what happens to the wavelength
the wavelength decreases
describe a translucent object
an object that allows light to pass through, but the light is scattered or refracted
describe a transparent object
object that transmits all the incident light that enters it
what are the three primary colours
green, red, blue
what are the three secondary colours
magenta, cyan, yellow
what happens when all colours reflect
a white light forms
what happens when a light enters a filter
A filter will only allow that specific colour to be transmitted.
It will absorb all other colours
decribe the focal point
the point where light rays parallel to the principal axis of a lens are focused (or appear to diverge from)
what is the principle axis
horizontal line in the middle of a ray diagram
what colour has the largest wavelength
red
what colour has the smallest wavelength
violet
what does colour and transparency depend on
the absorbed wavelengths
what are the three things that can happen to light rays when they hit an object
- absorbed
- trasmitted
- reflected
why are objects opaque
because they absorb some of the colours but reflect other colours
what colour do red and blue form
magenta
what colour do blue and green form
cyan
what colour do green and red form
yellow
why would an object be black
because they absorbe all wavelengths of visible light
what do colour filters do
they only let particular wavelengths of light through
what would a blue object appear as in a red filter
black
