Reflection of Light Flashcards
What is reflection of light
Light may be absorbed by the new medium, or transmitted onward through it or it may bounce back into the first medium. This ‘bouncing’ of light at an interface is called reflection
Laws governing reflection
1) The incident ray, the reflected ray and the normal to the reflecting surface all lie in the same plane
2) Angle of incidence, i, equals the angle of reflection, r
What is diffuse reflection
When parallel light encounters an irregular surface, it is scattered in many directions. It is by diffuse reflection that most objects (except self-luminous ones) are seen, e.g. furniture, etc. A perfect reflecting surface (free from irregularities causing diffuse reflection) would itself be invisible. Only the image formed by light reflected in it would be seen
Properties of image formed in reflection
It is upright (erect), virtual, and laterally inverted
It lies along a line perpendicular to the reflecting surface and is as far behind the surface as the object is in front of it
What happens to angles of incidence and reflection when a mirror is rotated
If a plane mirror is rotated while light is incident upon its centre of rotation, the reflected ray is deviated through an angle equal to twice the angle of rotation of the mirror.
New angle ICR2= 2a (a=angle of rotation of mirror)
What is a concave mirror
when the reflecting surface lies on the inside of the curve
What is a convex mirror
when the reflecting surface lies on the outside of the curve
What is the principal axis
An axis is any line passing through the centre of curvature and striking the mirror. That passing through the pole of the mirror is called the principal axis
Formula to calculate the position of image formed by the spherical mirror
1/v-1/u=1/f=2/r
u is the distance of the object from the mirror, v is the distance of the image from the mirror,
f is the focal length of the mirror, and
r is the radius of curvature of the mirror
Properties of image formed by concave mirror: object outside centre of curvature
Image real, inverted, diminished (reduced in size), lying between C and principal focus F.
Properties of image formed by concave mirror: object between centre of curvature and principal focus
Image real, inverted, enlarged, lying outside the centre of curvature C
Properties of image formed by concave mirror: object inside principal focus
Image erect, virtual and enlarged
What is the magnification formula of a curved mirror
i/o=-v/u
i=image size
o=object size
v=distance of image from mirror
u=distance of object from mirror
Clinical use of curved mirrors
The anterior surface of the cornea acts as a convex mirror and is used as such by the standard instruments employed to measure corneal curvature
What are catoptric images
Images formed by the reflecting surfaces of the eye
