LAB EXPERIMENT CORVERGING LENS PDF

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EXPERIMENT 3 :COVERGING LENSLECTURER :DR. NUR AMALINA MUSTAFFAGROUP MEMBERS :1) PUTERI EMY NABILAH BT AHMAD KHALIL (2020602606)2) NUR AININ SOFIYA BT ABD JALIL (2020476742)3) AHMAD FAIRUZ BIN MARZUKI (2020845108)DATE OF EXPERIMENT :11 th JUNE 2021DATE OF SUBMISSION :Depends on your submissionTitle :...

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EXPERIMENT 3 : COVERGING LENS

LECTURER : DR. NUR AMALINA MUSTAFFA

GROUP MEMBERS : 1) PUTERI EMY NABILAH BT AHMAD KHALIL (2020602606) 2) NUR AININ SOFIYA BT ABD JALIL (2020476742) 3) AHMAD FAIRUZ BIN MARZUKI (2020845108)

DATE OF EXPERIMENT : 11th JUNE 2021 DATE OF SUBMISSION :

Depends on your submission Title : CONVERGING LENS

Objective : 1. To determine the focal length of converging lens. 2. To investigate the formation of images by converging lens in different object position.

Theory A lens is a piece of transparent material bounded by two curved surfaces or a curved surface and a plane surface. Most lenses are made of glass and the curved surfaces are section of sphere. Some speacial lenses may have cylindrical surface. The lenses used in this experiment will all be spherical lenses.

If a beam parallel light strikes the surface of a lens it will be bent or refracted as shown in Figure 1. If the rays converge to a point as in Figure 1(a) the lens is called a converging lens. If the rays diverge as in figure 1(b) the lens is called a diverging lens. In either case the point through which the rays pass [Figure 1(a)] or from which they appear to come [Figure 1(b)] is called the principle focus of the lens, F, and the distance from this point to the lens is the focal lens,f.

If an object is placed in front of a converging lens an image will be formed. For a lens, the light passes through and the image, if real, will be formed on the side of the lens opposite from the object as shown in figure 2. Certain rays can be drawn to locate the image. One is the ray OAFI.

Since OA is parallel to the axis,O’C, after refraction it will pass through the focus,F. Another OCI, passes through the center of the lens and is unaffected. A third, OFBI passes through the focus F’, and refraction will be parallel to the axis. These three rays intersect at I and will locate the positions of the image II’. If another set of the similar rays were drawn from some other point on the object, they would locate a correspondig point on the image. If the object distance O’C, is called o and the image disctance, CI is called i, it can be proved for a thin lens (such will be used in this experiment) that

= ....................................................................(1) Where f is the focal length. According to Figure 2, o is considered positive on the left of the lens and negative on the right of the lens and i is positive in the right of the lens and negative on the left. The magnifications of lens, m, is equal to the ratio image size, II’to the object distance,OO’ m

= ........................................................................................(2)

which is also equal to ratio of the negative the image distance, i to the object distance,o,

m

= ........................................................................................(3)

The object size OO’ is considered positive when upright or erect and negative when inverted and likewise for the image II’. When the magnification, m, for single lens is negative, the image is inverted and real and when positive, the image is erect and virtual.

Procedure

(Refer video 3a and 3b) PART I: To estimate the focal length of converging lens using distant object 1. converging lens was placed on the optical bench with the screen near one end. 2. The object was pointed the benched at a distant and the image of a distant object on the screen was focussed. 3. The distance from the center of the lens to the screen was measured. Focal length, f of the lens was took as the approximate. 4. By equation (1), considering the focal length equal to the image distance was justified.

PART II: To determine the focal length of a converging lens using lens formula 1. The illuminated object was placed near one end of the bench and the screen on the other end. 2. The converging lens was placed between the object and the screen. 3. The lens moved until a sharp image is formed on the screen. 4. The distance of the object from the lens (o) and distance of the screen to the lens (i) was recorded. 5. The focal length, f of the lens by using equation (1) was calculated.The percentage difference between focal length obtained in part I and part II was calculated.

PART III: Image formation by converging lens at different position (far object, F1, 2F1, F2, 2F2 and O) 1. The illuminated lens was placed at near one end of the bench and the screen the other end. 2. The object was placed very far from lens and moved the screen until sharp image is formed on the screen. A same procedure for other position at F1, 2F1, F2, 2F2 and O repeated. Observation in a table was recorded. 3. Based on the experiment, draw the ray diagrams was drew for each case of study to show how the images are formed. The magnifications by equation (3) was computed.

Result and calculation PART I: To estimate the focal length of converging lens using distant object Calculation Distance lens = 50.7 cm Distance screen = 40.2 cm

PART II: To determine the focal length of a converging lens using lens formula Calculation Object distance = 90 – 76 = 14 cm Image distance = 76 – 40.5 = 35.5 cm

Percentage difference

PART III:Image formation by converging lens at different position (far object, F1, 2F1, F2,

2F2 and O) Case Object position,xo 1.

2.

Far object (∞)

Beyond 2F1 (50cm)

Observation Image Image position,x1 characteristi c At F2 Real, (20cm) Inverted, Highly diminished

Between F2 and 2F2

Real, Inverted, Diminished

Ray Diagram

Magnification M= -

M=-

=0

If o = 50cm,

= = i = 33.33 cm M= -

= -0.67 3.

At 2F1 (40cm)

At 2F2

Real, Inverted, Same size

If o = 40cm,

= = i = 40 cm M= -

= -1.00 4.

Between F1 and 2F1 (30cm)

Beyond 2F2

Enlarged, Inverted, Same size

If o = 30cm,

= = i = 60 cm M= -

= -2.00 5.

At F1 (20cm)

Very far (∞)

Real, Inverted, Highly Inverted

If o = 20cm,

= = i=∞ M= -∞

6.

Between F1 and lens (10cm)

No image form

If o = 10 cm

Virtual, Eract, Enlarged, Same size

= = i = -20 cm M= =2

Discussion

ERROR Parallex error The light is not turn off

PRECAUTION Make sure eyes perpendicular tu the scale of ruler Make sure turn off the light to get better image

Conclusion i) The focal length of convering lens is 10.0 cm ii)...