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Bài 2. Hướng dẫn THTN về hiện tượng phản xạ ánh sáng

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Nguồn: Sưu tầm
Người gửi: Lê Thái Trung (trang riêng)
Ngày gửi: 13h:13' 02-07-2008
Dung lượng: 2.8 MB
Số lượt tải: 17
Số lượt thích: 0 người

THE LAW OF REFLECTION
(P 32 01)
Apparatus
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 461
Diaphragm 1 and 2 slits
1

POG 400.03
Optical disc
1

POG 110
Plane mirror
1


Connecting lead
2

KAL 60/5A
Power supply
1

Procedure:
Put the plane mirror on the optical disk as shown.
The ray of light hits the mirror at point F. Point F is the center of the optical disk. The ray of light is reflected back on it self. The direction of this ray is termed the perpendicular.



Move the ray box until The ray hits the mirror at an angle ° .
The angle of incidence (the angle between the normal line (N) and the incoming ray). The angle of reflection (the angle between the normal line (N) and the reflected ray r) is seen to be 30° as well.

After experimenting with different angles of incidence and reading off the corresponding angles of reflection it may be found that:
the angle of incidence is always of the same magnitude as the angle of reflection .



ROTATING MIRROR
(P 32 02)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 461
Diaphragm 1 and 2 slits
1

POG 400.03
Optical disc
1

POG 110
Plane mirror
1


Connecting lead
2

KAL 60/5A
Power supply
1


Ruler
1


Whiteboard marker
1

Procedure:
Put the plane mirror on the optical disk as shown in the figure.
Draw N Perpendicular to the mirror with the whiteboard marker.
Position the the ray box so that the incoming ray hits point F and the angle of incidence is = 30°.


Rotate the mirror 10° and draw perpendicular N .


It can be observed that the reflected ray rotates 20°. In rotating the mirror by an angle an angle of incidence + ) and thus an angle of reflection + ) is produced.
The total deviation of the reflected ray is 2.

REGULAR REFLECTION
(P 32 03)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 462
Diaphragm 3 and 5 slits
1

POG 110
Plane mirror
1


Connecting lead
2

KAL 60/5A
Power supply
1

POF 220.01
Color filter, red
1

POF 220.02
Color filter, blue
1

Procedure:
Insert a diaphragm three slits into the ray box.
Setup the ray box and the mirror as shown in figure.
Place the color filter on outer light rays.
These three light rays represent a parallel beam of light.
Turn a parallel light rays as “V-shaped” to ilustrate the principle of regular reflection.



The parallel rays remain parallel to one another even after reflection, yet their order is reversed; after being reflected, the blue light ray can be found on the outside of the beam of light.














DIFFUSE REFLECTION
(P 32 04)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 462
Diaphragm 3 and 5 slits
1

POG 110
Plane mirror
1


Connecting lead
2

KAL 60/5A
Power supply
1


Scissors



Aluminum foil


Procedure:
The aluminum foil is first crumpled up, then wrapped around the plane mirror.
Place the mirror onto the adhesive magnetic board.
The parallel beam of light is reflected in every possible direction (diffracted, diffuse reflection).



The uneven surface of the aluminum foil can be thought of as a large number of small mirrors, inclined toward each other at varying angles.


IMAGE POINT ON A PLANE MIRROR
(P 32 05)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
2

POG 461
Diaphragm 1 and 2 slits
2

POG 110
Plane mirror
1

POG 480.02
Arrow, L=80 mm
1


Connecting lead
4

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1

Procedure:
Draw a straight line a using the whiteboard marker.
Place The two ray box are so that the two rays intersect at object point M and then reflected in the plane mirror.

The light rays proceeding from M are drawn in prior to and following reflection.
Since the reflected light rays do not intersect afterward, no real image point, instead merely a light spot, exists.

The observer`s eye is now drawn in.
It looks along the reflected light rays toward the mirror. The human eye does not perceive the "bend" along the path of the light rays but rather extends them further according to a straight line. The extensions of the reflected light rays intersect at the imaginary point M`.
M and M` lie symmetrical to each other about the same axis, the plane mirror.










VIRTUAL IMAGE ON A SMOOTH MIRROR
(P 32 06)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
2

POG 461
Diaphragm 1 and 2 slits
2

POG 110
Plane mirror
1

POG 480.02
Arrow, L=80 mm
1


Connecting lead
4

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1

Procedure:
Set up the experiment according to the figure.
Two parallel light rays proceed from the tip S and the foot F of the object G (arrow, l = 80 mm) which are then reflected back on themselves. These light rays and the extensions of the reflected rays are drawn in.



Turn the lower ray box so that the two light rays intersect at the tip S of the object.
The light ray proceeding from S, the reflected ray and its extension are drawn in. The result is the virtual image point S`.






Turn the upper ray box so that the two light rays intersect at the foot F of the object G.
The light ray proceeding from F, the reflected ray and its extension are drawn in. The result is the virtual image point F`. The virtual image B is an arrow from F` to S`.


CONCAVE MIRROR
(P 32 07)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
1

POG 461
Diaphragm 1 and 2 slits
1

POG 462
Diaphragm 3 and 5 slits
1

POG 101
Mirror, flexible
1


Connecting lead
2

KAL 60/5A
Power supply
1


Whiteboard marker
1


Ruler
1

Procedure:
Insert a diaphragm with one slit the ray box.
The point S is marked at a distance of 35 cm: this serves as the vertex of the concave mirror. The ends of the flexible mirror span points that lie at a distance of 6 cm perpendicular to the vertex, situated symmetrically to the optical axis (a=b).

Remove the diaphragm.
A narrow beam of light parallel to the axis is created. The rays of light reflected in the concave mirror result in a catacaustic curve, the apex of which is the focus F.

Measurement example:
Distance SF = f = 2.5 cm

Reverse the raybox, a divergent beam of light is generated which is then reflected from the concave mirror.


Insert the diaphragm with five slits.
Each of the focal points (i.e. the points where the reflected rays intersect the optical axis) is marked.

Concave mirrors consisting of sections of a circle (or, spatially speaking, sections of a sphere) do not have a single focal point but rather a focal spot. Ideally, the following holds true: distance SF = f = r 2 .

PATH OF RAYS IN A CONCAVE MIRROR
(P 32 08)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
2

POG 461
Diaphragm 1 and 2 slits
2

POG 101
Mirror, flexible
1


Connecting lead
4

KAL 60/5A
Power supply
1


Whiteboard marker
1


The light ray moving along the optical axis is reflected back upon itself from the vertex S. This ray represents a perpendicular. It is marked in with the whiteboard marker.
Another ray at an angle to the first one reaches the mirror at the vertex S. The Law of Reflection is demonstrated in this case.



The ray moving along the optical axis is reflected back upon itself. This is called a midpoint ray since it passes through the center of the circle.
The ray box 1 is used to create a light ray parallel to the axis and reaching the concave mirror at point P. Being reflected according to the Law of Reflection, this ray intersects the optical axis at the focal point F1. The reflected light ray PF1 is drawn in.









A ray of light traveling along the line F1P is reflected parallel to the optical axis.





IMAGES IN A CONCAVE MIRROR
(P 32 09)
Apparatus:
GSN 246
Adhesive magnetic board
1

POG 465
Ray box, 6V 20 W
2

POG 461
Diaphragm 1 and 2 slits
2

POG 480.01
Arrow, L=40 mm
1

POG 101
Mirror, flexible
1


Connecting lead
4

KAL 60/5A
Power supply
1


Whiteboard marker
1

Procedure:
Draw the optical axis and place the arrow as object G.
Use Ray box 1 to generate a light ray parallel to the optical axis and aimed at the tip of the object.
The light ray proceeding from ray box 2 is a midpoint ray and it is reflected back upon itself. The inverted, real image B is drawn where the two reflected rays intersect. The main ray, B, M and F are all drawn in.
The path of the rays shows how a real but smaller, inverted image is created.

The optical axis and the center of curvature M are drawn in, the concave mirror is mounted as shown.
An object 2 cm high is drawn in as shown in the figure.
Ray box 1 generates a light ray that travels parallel to the optical axis and is reflected through the focal point F. The object may be seen to be just beyond the focal length.
The light ray proceeding from the tip of G is drawn in.
Ray box 2 is used to create a light ray passing through the tip of G and the focal point F which
travels parallel to the axis after being reflected, in accordance with the Law of Reflection. The light ray is drawn in beginning from the tip of G. The real but inverted and magnified image B existswhere the two light rays intersect.


The vertex S and the optical axis are drawn in order to illustrate how a virtual image is created. The concave mirror is set up as shown in the figure. The object (G = 2 cm) is drawn in at a distance of 3 cm from the concave mirror.
Proceeding form ray box 1, a light ray parallel to the axis passes through the tip of object G. The light ray proceeding from G and the reflected ray are drawn in. Object G is found within the focal length.



Ray box 2 generates a light ray passing through the tip of the object and reaching the mirro
 
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