why is a convex lens called a converging lens
A lens is transparent block that causes light to refract (changes the direction the light travels in). A
converging lens (or convex lens) is curved on both sides. This means the light rays coming out of it come together at a point they converge. The point at which the light rays meet is called the focal point. The focal length is found by focussing a distant object on a piece of paper through the lens. The focal length is the distance between the centre of the lens and the image.
A converging lens is used in a refracting telescope to focus the image. Galileos telescope would have been a refracting telescope. The rays of light from the person are converged by the convex lens forming an image on the film or charged couple device in the case of a digital camera. The angle at which the light enters the lens depends on the distance of the object from the lens. If the object is close to the lens the light rays enter at a sharper angled.
This results in the rays converging away from the lens. As the lens can only bend the light to a certain agree the image needs to be focussed in order to form on the film. This is achieved by moving the lens away from the film. Similarly, if the object is away from the lens the rays enter at a wider angle. This results in the rays being refracted at a sharper angle and the image forming closer to the lens.
In this case the lens needs to be positioned closer to the film to get a focused image. Thus the real image of a closer object forms further away from the lens than the real image of a distant object and the action of focusing is the moving of the lens to get the real image to fall on the film. The image formed is said to be real because the rays of lighted from the object pass through the film and inverted (upside down).
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