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There are two type of lens which are concave and convex lense, formation of image can be done by these lenses
Typology: Lab Reports
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Name: Lab Partner: Section:
In this experiment, the formation of images by concave and convex lenses will be explored. The application of the thin lens equation and the magnification equations to single and compound lens systems will be investigated.
Lenses are common optical devices constructed of transparent material e.g. glass or plastic, which refract light in such a way that an image of the source of light is formed. Normally, one or both sides of the lens has a spherical curvature. When parallel light from a source impinges on a converging lens, the parallel rays are refracted so that all the light comes together at a focal point. The distance between the lens and the focal point is called the focal length of the lens. An imaginary line parallel to the light rays and through the center of the lens is called the principal axis. See Figure 10.1. Another basic type of lens is the diverging lens. With a diverging lens, parallel rays are spread out by the lens. The focus of a diverging lenses is on the same side of the lens as the impinging parallel rays. See Figure 10.1. The thin-lens equation relates the distance of the object from the lens, d (^) o , and the distance of the image from the lens, d (^) i , to the focal length of the lens, f. See Figure 10.2. The thin lens equation is: 1 d (^) o
d (^) i
f
The magnification equation is:
m =
Image Height Object Height
h (^) i h (^) o
d (^) i d (^) o
Figure 10.1: Converging lens (left) and diverging lens (right).
Figure 10.2: Geometry for the thin lens equation.
where h (^) o is the object height and h (^) i is the image height. The magnification, m, is the ratio of these heights. Since the triangle formed by the ray through the center of the lens and the object distance and height is a similar triangle to the triangle formed by the ray through the center of the lens and the image distance and height, the ratio of (^) hh (^) o^ i = - (^) dd^ i (^) o. The following sign conventions are used with the thin-lens and magnification equations:
When more than one lens is used, the thin lens equation can be applied to find the image location for the first lens. This location of the image from the first lens is then used as the object for the second lens and a second application of the thin lens equation. This process will be used in the last part of the experiment to investigate a concave lens. For the magnification equation for multiple lenses, the total magnification is the product of the magnifications of the individual lenses.
Light Source
Target Lens 75mm^ Screen
Cross Arrow
Figure 10.5: Arrangement of components for the approximate focal length measurement for a single lens.
the image, which will be very small, being at the focal length of the lens.
Distance between the lens and the screen (d (^) i )
Object distance (d 0 )
Focal length of lens % error
The magnetic optics rail contains a measuring scale along the side. The optics components mount on magnetic component holders. Each holder has a small indicator position on the side to locate the position of the component on the rail side scale (see Figure 10.4). Each component should be centered on the holder.
Calculated image distance d (^) i Calculated magnification Orientation
Measured image distance d (^) i % di↵erence between calculated and measured d (^) i Measured magnification % di↵erence between calculated and measured magnification
Light Source
CAT
concave convex −150 mm75 mm
.1 m^ .1 m
Screen
Figure 10.7: Compound lenses: The -150 mm focal length concave lens is placed in front of the 75 mm convex lens.
10.4 Conclusion
Write a detailed conclusion about what you have learned. Include all relevant numbers you have measured with errors. Sources of error should also be included.