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
- HI is 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
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.
ReplyDeleteNice explanations congratulations for all
ReplyDeleteGood
ReplyDelete