Monday, 29 August 2011

Reflection of light


Light:
v  Is the form of energy that enters our eyes
v  Enables us to see things
v  Can either be directly obtained from a luminous source or reflected off a non-luminous source into our eyes
v  A luminous source is an object that emits its own light such as the Sun
Reflection:
v  Incident ray
Ø  Ray of light that strikes the surface
v  Reflected ray
Ø  Ray of light that is reflected off a surface
v  Normal
Ø  Imaginary line that is perpendicular to the surface at the point of incidence
v  Angle of incidence
Ø  Angle between the incident ray and the normal
v  Angle of reflection
Ø  Angle between the reflected ray and the normal
Diffused reflection and specular reflection:
v  Diffused reflection
Ø  Reflected in all different directions
Ø  Produces a distorted image
v  Specular reflection
Ø  Reflected in the same direction
Ø  Produced a clear image
Image characteristics of mirror:
v  Image is formed in mirror as
Ø  Light rays reflect off you
Ø  Strikes the mirror
Ø  Goes back into your eyes
v  Image formed in  plane mirror
Ø  Has the same size as the object,
Ø  Is as far behind the mirror as the object is in front of the mirror,
Ø  Has the same orientation as the object (i.e. upright if the object is upright),
Ø  Is laterally inverted,
Ø  Is virtual.
v  Virtual image cannot be captured on a screen because no actual light rays meet at the image position.
v  Plane mirrors
Ø  Object position: anywhere
Ø  Image position: as far behind the mirror as the object is in front of it
Ø  Image type: virtual
Ø  Image orientation: same as object
Ø  Image size: same as object
v  Concave mirrors
Ø  Near mirror (inside F)
§  Image position: on the opposite side of the mirror as the object
§  Image type: virtual
§  Image orientation: same as object
§  Image size: larger than object (magnified)
Ø  Exactly at F
§  Image position: at infinity
§  Image type: -
§  Image orientation: -
§  Image size: -
Ø  Object distance less than     image distance (outside F)
§  Image position: on the same side of the mirror as the object
§  Image type: real
§  Image orientation: opposite of object
§  Image size: larger than object
Ø  Object distance is equal to image distance (outside F)
§  Image position: on the same side of the mirror as the object
§  Image type: real
§  Image orientation: opposite of object
§  Image size: same as object
Ø  Object distance greater than image distance (outside F)
§  Image position: on the same side of the mirror as the object
§  Image type: real
§  Image orientation: opposite of object
§  Image size: smaller than object
v  Convex mirrors
Ø  Object position: anywhere
Ø  Image position: on the opposite side of the mirror as the object
Ø  Image type: virtual
Ø  Image orientation: same as object
Ø  Image size: smaller than object

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