Please answer the following question: Information: - Binoculars or field glasses are binocular telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal mounted military models. - An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece. - Opera glasses, also known as theater binoculars or Galilean binoculars, are compact, low-power optical magnification devices, usually used at performance events, whose name is derived from traditional use at opera performances. Magnification power below 5 is usually desired in these circumstances in order to minimize image shake and maintain a large enough field of view. A magnification of 3 is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular lorgnettes of the 19th century. - A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and sometimes prisms ; the use of prisms resulting in a lightweight telescope . Volume and weight are less than half those of binoculars of similar optical properties , making it easy to carry , and also proportionally less expensive . Monoculars produce 2 - dimensional images , while binoculars add perception of depth ( 3 dimensions ) , assuming one has binocular vision . Monoculars are ideally suited to those with vision in only one eye , or where compactness and low weight are important ( eg hiking ) . However , monoculars are sometimes preferred by those with normal vision , where using both eyes through binoculars causes difficulties . A monocular with a straight optical path is relatively long ; prisms can be used to fold the optical path to make an instrument which is much shorter ( see the article on binoculars for details ) . Monoculars , sometimes called telescopes when used in this capacity , are used wherever a magnified 2 - dimensional image of a distant object is required ( Though some may be used to look at objects closer ) . Visually impaired people may use monoculars to see objects at distances at which people with normal vision do not have difficulty , e.g. , to read text on a chalkboard or projection screen . Applications for viewing more distant objects include natural history , hunting , marine and military applications . When high magnification , a bright image , and good resolution of distant images are required , a relatively large instrument is preferred , often mounted on a tripod . Smaller pocket - sized '' pocket scopes '' can be used for less stringent applications . Whereas there is a huge range of binoculars on the market , monoculars are less widely available and with less choice in the top quality bracket , with some traditionally very high quality optical manufacturers not offering monoculars at all . Today , monoculars are most commonly... - A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes the refracting telescope has been superseded by the reflecting telescope which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of the objective lens by that of the eyepiece. - A reflecting telescope (also called a reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope. - An optical telescope is a telescope that gathers and focuses light, mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct view, or to make a photograph, or to collect data through electronic image sensors. - The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated (parallel) rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more sharply, bringing them to a focus in a shorter distance. - Binocular vision is vision in which creatures having two eyes use them together. The word binocular comes from two Latin roots, "bini" for double, and "oculus" for eye. According to Fahle (1987), having two eyes confers six advantages over having one. - A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s, by using glass lenses. They found use in both terrestrial applications and astronomy. - Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term "glass", in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO), sodium oxide (NaO) from sodium carbonate (NaCO), calcium oxide, also called lime (CaO), and several minor additives. After reading the paragraphs above, we are interested in knowing the entity with which 'monocular' exhibits the relationship of 'subclass of'. Find the answer from the choices below. Choices: - aberration - amorphous solid - calcium oxide - camera - collecting - design - device - distance - electromagnetic spectrum - eye - field - field of view - focal length - glass - image - length - lens - light - material - name - opera - optical instrument - optical telescope - oxide - part - performance - photograph - point - quartz - reflecting telescope - reflector - refracting telescope - research - second - silicate - spy - system - telescope - theater - type - variety - vision - window - window glass
Answer:
optical instrument