Option C Imaging Flashcards
How do you draw the rays in a ray diagram (for lenses, mirrors too?)
Straight through lens (doesn’t change)
Parallel —> focal point
Focal point —> parallel
(When focal point always think which one (does it diverge or converge?), also not always actually through, but behaves as though through/from/to)
(Convex/Converging lens) If object within (closer than) the focal length, the image will be:
Virtual
Focal length
Distance from centre of lens to focal point
Convex Converging lens focal length neg or pos?
Focal length is ALWAYS POSITIVE
(Doesn’t matter on which side of the lens, always pos for converging lens)
Focal length neg or pos for concave diverging lens?
ALWAYS NEGATIVE!
Put -f in formula
Sign of focal length only dep the type of lens!!
Converging convex = POs
Diverging concave = neg
Object distance
Distance between the lens and object
Is object distance (do) POs neg?
Object distance always positive UNLESS multiple lenses, then could be neg
So basically ALWAYS POSITIVE FOR A SINGLE LENS (no matter concave or convex)
Image distance
Distance between centre of lens and image PARALLEL TO THE PRINCIPAL AXIS
What does the sign of the M (angular magnification) tell you about the image?
Whether it is up or down.
Positive M (due to neg di(not nec???)) means the image is
Right side up (not flipped). Not inverted
Neg M (pos di) means the image is
Upside down// image is inverted
What is the near point?
The smallest distance at which an object can be placed in order for the eye to form a clear image without straining. Generally said to be 25cm. (Double check if this is all)
What is the far point?
The furthest distance an object can be at to still see it/form a clear image of it (?) in theory infinity.
Image distance positive when
Image distance on OPPOSITE SIDE of the lens as the OBJECT distance
//
If image distance/image on the SAME SIDE AS THE EYE
Image distance neg when
Image distance on SAME SIDE of the lens as the OBJECT distance
//
If image distance/image on the OPPOSITE SIDE AS THE EYE
What does angle of incidence tell you about the reflected ray?
Angle of incidence=angle of reflection.
Angle is between light ray and normal
What do dotted lines mean in a ray diagram?
Not real, virtual, rays.
Focal point in relation to centre of curvature (mirrors)
Centre of curvature = 2f
Or focal point = half C
How do you draw ray diagram for concave mirror?
Top of object parallel to mirror (reflected) then —> through focal point. (If ray parallel, will go through focal point when reflected)
From top of object through the focal point, reflect, —> parallel
OBS IF THÉ OBJECT IS NOT ON THE PRONCIPAL AXIS, YOU MUST ALSO DRAW FROM THE BOTTOM OF THE IBJECT!!!!!
Image of concave mirror w object outside of focal length, further away or at c
Inverted (smaller at far distance, but at C same size I think and approaching focal length increases in size (larger than object))
Concave mirror object IN (closer than) focal length: image?
Parallel to focal fine
Focal —> parallel: go “from behind” through focal then object then image
Lines diverge, draw dotted virtual “into” the mirror,
VIRTUAL, LARGER, UPRIGHT image.
Convex mirror ray diagram
Top of object
Parallel —> focal point
Focal point —> parallel
(Not actually through f, virtual lines)
Divergence outside mirror, convergence virtual, virtual upright smaller image (at least in the example)
Double check so that angle incidence = angle reflection
Does the thin lens formula (1/f = 1/do + 1/di) tell you anything about size of the image//object or non-horizontal distances
ONLY GIVES HORIZONTAL DISTANCES!
To know heights use angular magnification formula M = - di/do
