Wednesday, October 11, 2017

PHYSICS || PROJECTION LANTERN


The Structure of the Projection Lantern
Describe the structure of the projection lantern
The projection lantern forms images of slides or camera film onto a distant screen. The film or slide to be projected is inverted and highly illuminated.
The Mode of Action of a Projection Lantern
Describe the mode of action of a projection lantern
Optical arrangement of projection lantern.
  • The slice or film to be projected is inverted and highly illuminated.
  • The concave mirror helps to concentrate the light which would otherwise be partly wasted.
  • The lamp is placed at the principal focus of the concave mirror.
  • The heat filter reduces the heat at falling on the slide or film so as to avoid it overheating.
  • Since the image of the projection lantern is Highly magnified, it would not be very bright if there was not enough illumination.
  • The condenser directs a maximum amount of light from the source of the slide and produce uniform illumination the screen. (The condenser is a double in order to reduce chromatic aberration).
  • The projection lens forms the image of the slide on the screen.
  • The light source is usually located at a distance of 2f from a condenser and invited so that the image on the screen is upright (erect).
  • The focal length of the projection lens is ABOUT TWICE THE FOCAL length of the condenser since the screen is usually far from the lens.
The Magnification of a Projection Lantern
Determine the magnification of a projection lantern
Example 4
A lantern projector using a slide of (2cm x 2cm) projects a picture (1cm x 1cm) onto a screen 12m from the projection lens. How far from the lens must the slide be? Find the approximate focal length of the projection lens.
Solution
The magnification m is given by;
M = V/U ………………………………………i
Where
  • His the size of image
  • H is the size of object
  • U object distance
  • V image distance
Thus
M = Hi …………………. ii
Then eqn (i) = eqn ii
  • v/u =hi/h
  • (1200/u)-1 = (100/2) -1
  • (u/1200) = (2/100)
  • U = (2/100) (1200)
  • U = 24cm
The object distance, U = 24cm
Uses of a Projection Lantern
Mention uses of a projection lantern
Projection lantern are used in various areas. These include:
  • Projection of films, slides and transparencies,
  • projection of opaque objects, i.e. episcopic projection,
  • used in searchlights and headlights,
  • used in projection apparatus in industry for gauge and screw thread testing,
  • used in physical experiments such as projection of a spectrum,
  • used in polarisation experiments and interference experiments.
A Simple Projection Lantern
Construct a simple projection lantern
Projection Lantern
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3 comments:

  1. This is very helpful for me but i want more info about LED projection Light because i am writing thesis on projection light so kindly help me.

    ReplyDelete
  2. Nice explanations congratulations for all

    ReplyDelete

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