While drawing images of the object, we benefit from the special rays given above. We use them because we know the paths of them. Let’s start drawing images of the objects located in different parts of the mirror.
1. If the object placed at the center of the mirror, an image is also formed at the center, real, inverted and with the same size as the object. To find this image we send two rays from the top of the object. One of them is parallel to the principal axis which passes from the focal point after reflection and the second ray passes from the focal point and goes parallel to the principal axis after reflection. The intersection point of these two reflected rays gives us the location of the image. As you can see from the picture green one is an image of the object.
2. If the object placed away from the center of the mirror, an image is formed between the focal point and center of the mirror. Properties of mirrors are, real, inverted and reduced in size.
3. If the object placed between the focal point and center of the mirror, then the image is formed away from the center. Characteristics of the image are; real, inverted and magnified in size.
4. In this picture object is placed at the focal point and as you can see reflected rays goes parallel to each other. In other words, they do not intersect in any point, thus, we assume that image is formed at infinity.
5. If the object placed between the focal point and vertex then a virtual image is formed behind the mirror. Since the rays reflected from the mirror do not intersect, their extensions behind the mirror intersect and the virtual image is formed. Image is magnified in size and erect, unlike the real images.
Example: Look at the given picture, If the distance between the object and its image is 120cm, find the focal length of this mirror. Image of the object is behind the mirror, erect and its length is three times larger than the object.
Example: We have an optical system including a concave mirror and a plane mirror in the picture given below. Object is located at point A; its first image is formed in the plane mirror and the second one is in a concave mirror. Find these images of the object.
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