OPTICS

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OPTICS

• The study of light

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Light - electromagnetic waves In the visible
range, having a wavelength from about 400
nanometres in the extreme violet to about 770
nanometres in the extreme red. Light
is considered to exhibit particle and wave
properties,and the fundamental particle,
or quantum, of light is called the photon.The
speed of light (and of all electromagnetic
radiation) in a vacuum is approximately 300,000
km/186,000 mi per second, and is a
universal constant denoted by c.
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Range of frequencies

• Different colour sensations are produced by light
  vibrating at different frequencies, ranging from
  about 4 1014 vibrations per second for red
  light to about 7.5 1014 vibrations per second
  for violet light. The visible spectrum of light
  is usually defined by its wavelength, ranging
  from the smallest visible wavelength for violet,
  about 40 millionths of a centimetre (16
  millionths of an inch), to 75 millionths of a
  centimetre (about 30 millionths of an inch) for
  red. Higher frequencies, corresponding to shorter
  wavelengths, comprise ultraviolet radiation, and
  still higher frequencies are associated with
  X-rays. Lower frequencies, which are at longer
  wavelengths, are called infrared radiation, and
  still lower frequencies are characteristic of
  radio waves. Most light comes from electrons that
  vibrate at these high frequencies when heated to
  a high temperature. The higher the temperature,
  the greater the frequency of vibration and the
  bluer the light produced.

• .

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THE SOURCES OR LIGHT
The sources of light are all objects emitting
their own light. The most powerful of those
objects are the stars. There are also other
objects emitting light mainly due to

• Heating up the material to high temperatures (the
  bulb)
• Stimulation of gas particles in a strong electric
  field (the neonlamp)
• Absorbing ultraviolet radiation (luminofor),
• Chemical reactions (the candle light).

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How the light travels

• Light is emitted from a source in straight lines
  and spreads out over a larger and larger area as
  it travels the light per unit area diminishes as
  the square of the distance. When light strikes an
  object, it is either absorbed or reflected light
  reflected from a rough surface is scattered in
  all directions. Some frequencies are reflected
  more strongly than others, and this gives objects
  their characteristic colour.

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The reflection of light
White surfaces scatter light of all wavelengths
equally, and black surfaces absorb nearly all
light. Image-forming reflection, on the other
hand, requires a highly polished surface such as
that of a mirror.
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Objects that are not sources of light can be seen
by us, because the light that hits them scatters
and some of the rays reach our eyes.
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IMAGES IN THE MIRROR
The image that can be seen in a mirror is a
relative one symetric to the surface of the
mirror. It is relative to the surface of the
mirror. Should it change, the image would be
distracted (false mirrors).
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SPHERICAL MIRRORS
A spherical mirror is a part of the surface of a
polished part of a sphere. There are several
kinds of spherical mirrors

• Concave when the reflecting part is the inner
  part of the sphere.
• Convex when the reflecting part is the outer
  part of the sphere.

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• Each spherical mirror has
• The center of the carvature
• The radius of the carvature
• The central axis

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REFLECTIONS IN THE CONCAVE MIRROR
The parrallel rays of the light hitting the
concave surface of the mirror reflect and
subseqently cross at the point known as the focus
point. That point is located on the main axis of
the mirror. The distance between the focus point
and the surface of the mirror is called the focus
distance.
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REFLECTIONS IN THE CONVEX MIRROR
The convex mirror has an apparent focus. The
parallel rays after hitting the mirror become
scattered and reflected at a certain angle.
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SCATTERING OF THE LIGHT
The scaterring of light is a proces in the the
light changes its direction after penetrating a
transparent object. The change in the direction
is caused by the fact that light traveles at
different speeds in different enviroments.
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Separation of White Light into
Colours
Light from many sources, such as the sun, appears
white. When white light passes through a prism,
however, it separates into a spectrum of varied
colours. The prism bends, or refracts, light of
different colours at different angles. Red light
bends the least and violet light bends the most.
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LENS

• A lens,in optics, is a piece of transparent
  material, such as glass, with two polished
  surfaces one concave or convex, and the other
  plane, concave and convex that modifies rays of
  light. A convex lens brings rays of light
  together a concave lens makes the rays diverge.
  Lenses are essential to glasses, microscopes,
  telescopes, cameras, and almost all optical
  instruments.
• The image formed by a single lens suffers
  from several defects or aberrations, notably
  spherical aberration, in which a straight line
  becomes a curved image, and chromatic aberration
  in which an image in white light tends to have
  coloured edges. Aberrations are corrected by the
  use of compound lenses, which are built up from
  two or more lenses of different refractive index.

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IMAGES RECIEVED THROUGH LENSES
When the light hits a lens it goes through it
and creates an image on the other side.

• Focal length is measured in two ways in ordinary
  units of length, as for example 20 cm or 1 m or
  in units called dioptres, equal to the reciprocal
  of the focal distance measured in metres. A
  1-dioptre lens has a focal length of 1 m (3.28
  ft) a 2-dioptre lens has a focal length of 0.5 m
  (1.64 ft). The ratio of the focal length to the
  diameter of a lens determines its light-gathering
  power or speed. This ratio is the so-called
  f-number of the lens.
• .

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• The ray parallel to the optical axis of the lens
  after penetrating the lens goes through its
  axis
• The ray going through the focus pointafter
  penetrating the lens becomes a parallel one to
  the axis of the lens
• The ray going the center of the lens doesnt
  change its direction on the other side of the
  lens.

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This presentation was prepared by
Agnieszka Bukowiecka