2. Reflection of Light Flashcards
what can happen to light when it meets an interface between two media
absorbed
transmitted
reflected
laws of reflection
incident ray, reflected ray and the normal to the reflecting surface all lie in the same plane
angle of incidence
equals the angle of reflection
parallel light and irregular surface
gets scattered in many directions –> diffuse reflection
brain and ‘images’
brain assumes that an objected is situated in the direction form which lights enters the eye BUT if the observer actually goes to the point of the image – there is no real image
virtual images
could not be captured on a screen
((usually dotted line
real images
could be captured on a screen
image formed at a plane surface is
erect
virtual
laterally inverted
if a plane mirror is rotated
the reflected ray is deviate through an angle equal to TWICE the anlge of ROTATION of the mirror
spherical mirror
is the reflecting surface is a portion of a sphere
if the reflecting surface lies on the inside of the curve
concave
if the reflecting surface lies on the outside of the curve
convex
centre of curvature
= C
the centre of the circle (is the reflecting surface was extended to a whole circle)
pole of the mirror
= p
centre of the reflecting surface
radius of curvature
= r
distance between C to P
axis
axis is any line passing through the centre of curvature and striking the mirror
principle axis
an axis passing through the centre curvature and striking the mirror AT THE POLE
rays parallel to the principle axis are reflected
concave = towards the principal focus
convex = away from the principal focus
principal focus
= F
this is the mid point of r (radius of curvature)
mid point between C and P
focal length
= f (lower case)
distance between F and P
half the radius of the curvature
an object situated on the principal axis at infinity
is formed on at the principal focus
image formed by a concave mirror
real (infrontof lens)
image formed by a convex mirror
virtual (behind lens)
how to construct a ray diagram
- Ray parallel to principal axis reflected to/away from principal focus
- Ray from top of object passing through the centre of curvature and reflected back
CONCAVE mirror
object outside C
real
inverted
diminished
CONCAVE mirror
object between C and P
real
inverted
enlarged
CONCAVE mirror
object inside principal focus
erect
virtual
enlarged
CONVEX mirror
object at any point
virtual
erect
diminished
position of the image formed calculation
1/v - 1/u = 1/f = 2/r
u = distance of the object from the mirror
v = distance if the image from mirror
f = focal length
r = radius of curvature
definition of magnification
ratio of image size to object size
magnification calculation
i / o = - (v / u)
i = image size
o = object size
v = distance of object from mirror
u = distance of image from mirror
sign convention
distances measured in the same direction as the incident lgiht are positive
against the direction are negative
all distances are measured
from the pole of the mirror to the point in questions
image size is postive for
erect images (above the principal axis)
image size is negative for
inverted images (below the prinicpal axis)
Purkijne image I
Anterior cornea
Image - erect and virtual
Use - squint, keratometer
Purkijne image II
Posterior cornea
Image - erect and virtual
Use - specular microscopy
Purkijne image III
Anterior lens
Image - erect and virtual
Use - lens in accom
Purkijne image IV
Posterior lens
Image - real and inverted
Use - lens in accom
