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Bài 6. Hướng dẫn THTN về sự tạo ảnh qua hệ thấu kính

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Nguồn: Sưu tầm
Người gửi: Lê Thái Trung (trang riêng)
Ngày gửi: 11h:44' 08-06-2009
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PATH OF RAYS IN A SINGLE LENS
REFLEX CAMERA
(P 36 01)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 462
Diaphragm 3 and 5 slits
1

POG 240.02
Plan-convex lens model
1

POG 310.03
Prism, right angle
1

POG 110
Plane mirror
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1


A lamp projecting three parallel rays of light is set up near the left-hand edge of the panel. This arrangement symbolizes the light reflected from a remote object.
The plan convex lens is set up as shown in the figure. This symbolizes the objective lens of the camera. When the camera is focused properly, the remote object is projected as a virtually sharp point on the photographic film.
The position of the film is drawn in.

The view-finder is used to locate the desired image. The technique used in the case of the single lens reflex camera is shown.
Before reaching the film, the light rays entering are reflected upwards by a plane
mirror inclined at an angle of 45and then refracted toward the observer`s eye by a totally reflecting prism.
To demonstrate this, the right-angled prism with equal sides is applied as shown in the figure. The plane mirror is placed so that the light rays are reflected upwards and totally reflected at the hypotenuse of the inverting prism (see figure).
When the diaphragm is released, the plane mirror flips out of the way, allowing the light rays projected by the object to reach the film.





































PATH OF RAYS IN A SLIDE PROJECTOR
(P 36 02)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 462
Diaphragm 3 and 5 slits
1

POG 240.02
Plan-convex, lens model
2

POG 251
Semicircle, lens model
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1


The optical axis is drawn in.
The two plan convex lenses and the semi-circular model serving as the focusing lens are set up as shown in the figure. The pin in the lamp is pulled out so that it projects a divergent light beam.
The path of the light rays is observed once the lamp is switched on. The two planoconvex lenses serve as a condenser (light-gathering system). They ensure that the slide is completely illuminated (draw in object G).
Furthermore, it may be observed that the condenser projects the lamp filament onto the focusing lens (intertwined image). The focusing lens then produces an upright, real and magnified image of the slide on the screen.



If the condenser is removed, it may be observed how poorly the divergent light beam projected by the light illuminates the slide.















MODEL OF A MICROSCOPE
(P 36 03)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 461
Diaphragm 1 and 2 slits
1

POG 240.02
Plan-convex, lens model
2

POG 251
Semicircle, lens model
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1


First, the optical axis is drawn in and a biconvex lens is formed using the two plan convex lenses. The objective and ocular lens are positioned as well as the lamp as shown in the figure. The point where the two divergent light rays originate is taken as the object point.
The objective lens creates a real image point B which the ocular lens projects onto the eye`s retina. The two light rays proceeding from the ocular lens travel approximately parallel to each other so that the eye can view the image almost relaxed. Extending these rays leads to the observation that the microscope serves to increase the angle of vision.




























MODEL OF AN ASTRONOMICAL TELESCOPE
(P 36 04)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 461
Diaphragm 1 and 2 slits
1

POG 240.02
Plan-convex, lens model
1

POG 251
Semicircle, lens model
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1


First, the optical axis is drawn in.
The light as well as the objective and ocular lenses are set up as shown in the figure. The light rays proceeding parallel from the lamp symbolize light proceeding from a distant object. The convex, objective lens with a longer focal length than the ocular lens produces a real image point virtually at the focal point of the objective lens. The ocular lens projects this onto the retina.

The fact that the light rays travel parallel allows the eye to view the object almost relaxed. By extending these light rays, it can be seen how the telescope increases the angle of vision.













MODEL OF A GALILEAN TELESCOPE
(P 36 05)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 462
Diaphragm 3 and 5 slits
1

POG 240.02
Plan-convex, lens model
1

POG 260.02
Plan-concave, lens model
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1


First, the optical axis is drawn in.
The light as well as the objective and ocular lenses are set up according to the figure. The parallel light rays originating in the lamp represent light coming from a relatively far distant object. They reach the optical system at the angle of vision The objective lens focuses the light rays.
Before being focused at the object point, they are dispersed by the concave lens, thus leaving the system parallel once again. These light rays are perceived by the eye which can thus remain relatively relaxed. This demonstrates that the telescope increases the angle of vision > a).


The second experiment shows how the Galilean telescope is a telecentric system. Parallel rays of light entering this system leave it parallel once more. The diameter of the light beam is reduced, while the light density increases.

The length of the telescope is determined by the difference between the two focal lengths, since the focal point behind the convex lens coincides with the focal point in front of the concave lens.
 
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