Practical 4
Practical 4
Title: To study the magnification of a real image by a convex lens.
Objective: To determine the focal length of a convex lens.
Apparatus and Materials: 1. Light box 2. Convex lens 3. Plasticine 4. Meter rule 5. Screen 6. Short transparent ruler
Setup:
1. Set up the apparatus as shown in Figure 4-1.
Figure 4-1
Theory:
From the lens equation:
Where: p = object distance q = image distance
Linear magnification,
Procedure: 1. The apparatus was set up as in Figure 4-1. 2. The light source was switched on. 3. A length of “1cm” on the scale of the transparent ruler was chose as the object, therefore object size, y = 1cm. 4. A value for the object distance, p was set. The image distance was adjusted until a sharp image was obtained on the screen. 5. The image distance, q was measured. 6. The length, y’ or size of the “1cm” image was measured. 7. The magnitude of the linear magnification, m was found for each image where
.
8. The object distance was varied, steps 4 to 7 was repeated, and seven (7) sets of readings of p, q, y’ and m was obtained. 9. The readings of p, q, y’ and m was tabulated. 10. A graph of m against q was plotted. 11. The gradient of the graph was determined. 12. The focal length, f of the lens was calculated.
Data:
Size of object, y = ( 2.60 ± 0.10 ) cm Object distance,p ± 0.10cm | Image distance,q ± 0.10 cm | Size of image,y' ± 0.10 cm | Magnification,m = y’/y | 15.0 | 30.0 | 5.20 | 2.00 | 20.0 | 20.0 | 2.70 | 1.00 | 25.0 | 16.7 | 1.70 | 0.70 | 30.0 | 15.0 | 1.30 | 0.50 | 35.0 | 14.0 | 1.00 | 0.40 | 40.0 | 13.3 | 0.80 | 0.30 | 45.0 | 12.9 | 0.60 | 0.20 |
Calculation: Mean of image distance, q=30.0+20.0+16.70+15.0+14.0+13.3+12.97 = 121970 = 17.41 cm #
Mean of magnification, m, =2.00+1.00+0.70+0.50+0.40+0.30+0.207
Title: To study the magnification of a real image by a convex lens.
Objective: To determine the focal length of a convex lens.
Apparatus and Materials: 1. Light box 2. Convex lens 3. Plasticine 4. Meter rule 5. Screen 6. Short transparent ruler
Setup:
1. Set up the apparatus as shown in Figure 4-1.
Figure 4-1
Theory:
From the lens equation:
Where: p = object distance q = image distance
Linear magnification,
Procedure: 1. The apparatus was set up as in Figure 4-1. 2. The light source was switched on. 3. A length of “1cm” on the scale of the transparent ruler was chose as the object, therefore object size, y = 1cm. 4. A value for the object distance, p was set. The image distance was adjusted until a sharp image was obtained on the screen. 5. The image distance, q was measured. 6. The length, y’ or size of the “1cm” image was measured. 7. The magnitude of the linear magnification, m was found for each image where
.
8. The object distance was varied, steps 4 to 7 was repeated, and seven (7) sets of readings of p, q, y’ and m was obtained. 9. The readings of p, q, y’ and m was tabulated. 10. A graph of m against q was plotted. 11. The gradient of the graph was determined. 12. The focal length, f of the lens was calculated.
Data:
Size of object, y = ( 2.60 ± 0.10 ) cm Object distance,p ± 0.10cm | Image distance,q ± 0.10 cm | Size of image,y' ± 0.10 cm | Magnification,m = y’/y | 15.0 | 30.0 | 5.20 | 2.00 | 20.0 | 20.0 | 2.70 | 1.00 | 25.0 | 16.7 | 1.70 | 0.70 | 30.0 | 15.0 | 1.30 | 0.50 | 35.0 | 14.0 | 1.00 | 0.40 | 40.0 | 13.3 | 0.80 | 0.30 | 45.0 | 12.9 | 0.60 | 0.20 |
Calculation: Mean of image distance, q=30.0+20.0+16.70+15.0+14.0+13.3+12.97 = 121970 = 17.41 cm #
Mean of magnification, m, =2.00+1.00+0.70+0.50+0.40+0.30+0.207