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Form 4 Physics Questions and Answers on Thin Lenses
State what it is meant by the term accommodation as applied to the human eye
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1.
An object placed in front of a convex lens of focal length 10cm produces an image at a distance of 15cm from the lens and on the same side as the object. Determine the position of the object.
2.
(a) Draw a ray diagram to show how a convex lens works as a magnifying glass. (b) The diagram in figure 3 shows a certain eye defect. (i) Name the defect. (ii) Draw on the same diagram an arrangement to correct the defect.
3.
Fig. 8 shows an object O placed in front of a concave lens with principal foci F and F’. Construct a ray diagram to locate the position of the image.
4.
Fig. 2 drawn to scale, shows a lens L1 placed 30cm from an object O. The image is formed on the screen S 50cm from the lens. On the figure, draw appropriate rays then determine the focal length of the lens.
5.
Sketch a diagram to show the position of an object, when a converging lens is used as a magnifying glass.
6.
Figure 21 shows a converging lens whose focal point F is marked. An object is placed in front of the lens such that a real magnified image is formed by the lens. Sketch on the same diagram, a ray diagram to represent this.
7.
Figure 13 represents an object O placed 10cm in front of a diverging lens. F is the focal point of the lens. Draw rays to locate the position of the image. Determine the image distance.
8.
Figure 10 (drawn to scale) shows an image L formed by a diverging lens, L. On the same diagram, draw appropriate rays to locate the position of object. Determine the object distance.
9.
(a) Figure 8 shows an experimental set-up consisting of a mounted lens L, a screen S, a meter rule and a candle. (i) Describe how the set-up may be used to determine the focal length, f, of the lens. (ii) State the reason why the set-up would not work if the lens were replaced with a diverging lens (b) The graph in figure 9 shows the relationship between #1/u# and #1/v# for a converging lens where
10.
A vertical object is placed at the focal point F of a diverging lens as shown in figure 16. Sketch a ray diagram to show the image of the object.
11.
An illustrated vertical object is initially placed on the principal axis of a converging lens and 32cm from it. The focal length of the lens is 15cm. The object is now placed at a point 12cm from the lens and on the same side. State two changes other than magnification that are observed on the image formed due to this change.
12.
A vertical object is placed 20cm in front of a convex lens of focal length 5cm. (i) Determine: (I) The image Distance (II) The magnification. (ii) State two characteristics of the image.
13.
State what it is meant by the term accommodation as applied to the human eye
14.
(a) Figures 11 (a) and (b) show diagrams of the human eye. (i) Sketch in figure 11 (a) a ray diagram to show short sightedness. (ii) Sketch in figure 11 (b) a ray diagram to show how lens can be used to correct the short sightedness. (b) Figure 12 shows the features of a simple camera. (i) Name the parts labeled A and B. (ii) A still object is placed at a certain distance from the camera. Explain
15.
The diagram in figure 2 shows an object O laced in front of a converging lens. F and F’ are the principal foci for the lens. The object is now moved along the principal axis until a virtual image is produced. On the same diagram: (i) Draw the object O in the new position along the principal axis. (ii) Sketch rays to show formation of the virtual image.
16.
Figure 7 shows how rays from a distant and a near object are focused inside a human eye with a certain defect. Name the defect and state the cause of this defect.
17.
In an experiment, a pin, a converging lens and a plane mirror are arranged as shown in figure 4. The distance between the pin and the plane mirror is L cm while the distance between the lens and the plane mirror is q cm. The position of the pin is adjusted until its tip coincides with its real image. State the focal length of the lens.
18.
(a) State the meaning of the term “principal focus” as applied in lenses. (b) You are provided with the following apparatus to determine the focal length of a lens; A biconvex lens and lens holder, a lit candle, a white screen, a meter rule. (i) Draw a diagram to show how you would arrange the above apparatus to determine the focal length of the lens (ii) Describe the procedure you would follow.
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