Question

An optical device used by watch repairers is ________?

Answer 1

It is important to grasp all of the available information from a question. If we use the right approach and think why watch repairs need an optical device to look at the small components of a watch then we can arrive at the right answer.

Complete step by step answer:
The watch repairers need an optical device that can enlarge or magnify the small parts and components of a wrist watch so that it is easier for them to repair or change those particular components or pieces of machinery. A convex lens or popularly known as magnifying glass helps to produce magnified images of small objects so that it is easier to observe them. A magnifying glass (convex lens) utilizes a solitary focal point for amplification or magnification.
Thus an optical device that is usually used by watchmakers is a magnifying glass (convex lens).

Additional Information: The magnification that is produced by a convex lens depends on the distance between the point of observation (eye) and the object under view. The highest magnification is obtained when the placement of the lens is very close to the eye while gradually moving it away so as to get maximum focus. This ensures that a sharp image is obtained. 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.

Note: Students usually get confused between a convex lens and a concave lens as they both sound alike. It must be noted that their characteristics are quite opposite to each other. A convex lens is a diverging lens whereas a concave lens is a converging lens. It is because the converging character of a convex lens is why we can use it as a magnifying glass to view small objects.