Concave mirrors are used in reflecting telescopes.[5] They are also used to provide a magnified image of the face for applying make-up or shaving.[6] In illumination applications, concave mirrors are used to gather light from a small source and direct it outward in a beam as in torches, headlamps and spotlights, or to collect light from a large area and focus it into a small spot, as in concentrated solar power. Concave mirrors are used to form optical cavities, which are important in laser construction. Some dental mirrors use a concave surface to provide a magnified image. The mirror landing aid system of modern aircraft carriers also uses a concave mirror.

For convex mirrors, if one moves the 1 / d o {\displaystyle 1/d_{\mathrm {o} }} term to the right side of the equation to solve for 1 / d i {\displaystyle 1/d_{\mathrm {i} }} , then the result is always a negative number, meaning that the image distance is negative—the image is virtual, located "behind" the mirror. This is consistent with the behavior described above.

Convex mirrors are used in some automated teller machines as a simple and handy security feature, allowing the users to see what is happening behind them. Similar devices are sold to be attached to ordinary computer monitors. Convex mirrors make everything seem smaller but cover a larger area of surveillance.

The standard compound light microscope has 3 objective lenses to provide different magnification powers, resolving abilities, and fields of view to visualize specimens in increasing detail.

Most curved mirrors have a spherical profile.[7] These are the simplest to make, and it is the best shape for general-purpose use. Spherical mirrors, however, suffer from spherical aberration—parallel rays reflected from such mirrors do not focus to a single point. For parallel rays, such as those coming from a very distant object, a parabolic reflector can do a better job. Such a mirror can focus incoming parallel rays to a much smaller spot than a spherical mirror can. A toroidal reflector is a form of parabolic reflector which has a different focal distance depending on the angle of the mirror.

What is the objective lens of a microscopegive

The standard compound microscope contains 3 objective lenses with different powers, resolutions, and fields of view to provide a tiered viewing experience.

The 40x or 100x high power objective produces the highest magnification and resolution to reveal subcellular structures and other intricate details not discernable with the lower powered lenses but has an extremely narrow field of view. It is used for critical inspection of key areas after initial surveys with lower-powered objectives.

Objective lensfunction

The image on a convex mirror is always virtual (rays haven't actually passed through the image; their extensions do, like in a regular mirror), diminished (smaller), and upright (not inverted). As the object gets closer to the mirror, the image gets larger, until approximately the size of the object, when it touches the mirror. As the object moves away, the image diminishes in size and gets gradually closer to the focus, until it is reduced to a point in the focus when the object is at an infinite distance. These features make convex mirrors very useful: since everything appears smaller in the mirror, they cover a wider field of view than a normal plane mirror, so useful for looking at cars behind a driver's car on a road, watching a wider area for surveillance, etc.

Boxes 1 and 3 feature summing the angles of a triangle and comparing to π radians (or 180°). Box 2 shows the Maclaurin series of arccos ⁡ ( − r R ) {\displaystyle \arccos \left(-{\frac {r}{R}}\right)} up to order 1. The derivations of the ray matrices of a convex spherical mirror and a thin lens are very similar.

By convention, if the resulting magnification is positive, the image is upright. If the magnification is negative, the image is inverted (upside down).

A second ray can be drawn from the top of the object, parallel to the optical axis. This ray is reflected by the mirror and passes through its focal point. The point at which these two rays meet is the image point corresponding to the top of the object. Its distance from the optical axis defines the height of the image, and its location along the axis is the image location. The mirror equation and magnification equation can be derived geometrically by considering these two rays. A ray that goes from the top of the object through the focal point can be considered instead. Such a ray reflects parallel to the optical axis and also passes through the image point corresponding to the top of the object.

Certain instruments are designed to accommodate additional high-power 60x or 100x objective lenses when extremely high magnification and resolution are critical, such as for cytology or microbiology applications.

Some microscopes include extra low power 1x or 2x objectives for an even wider field of view to help orient the largest samples. These have become more common on inverted microscopes.

Whatarethe3objectivelenses ona microscope

Having a continuum of magnifications allows the microscope to accommodate samples of vastly different sizes from whole insect bodies down to single cells. A single high-power objective cannot cover this entire range.

The level of microscope magnification depends on the optical properties of both the ocular and objective lenses. The ocular lens magnifies the primary image 10x. The objectives provide progressively higher magnifying power of 4x, 10x, 40x, and sometimes 100x.

High-performance objectives may have adjustable correction collars to optimize the optical correction for viewing specimen slides with different coverslip thicknesses, allowing the best possible image.

The passenger-side mirror on a car is typically a convex mirror. In some countries, these are labeled with the safety warning "Objects in mirror are closer than they appear", to warn the driver of the convex mirror's distorting effects on distance perception. Convex mirrors are preferred in vehicles because they give an upright (not inverted), though diminished (smaller), image and because they provide a wider field of view as they are curved outwards.

The compound light microscope is an indispensable tool used ubiquitously in science disciplines to visualize small objects in fine detail. Unlike simple magnifying glasses, the compound microscope uses two lens systems to enlarge specimens up to 1000x their actual size.

Objective lensmagnification

These mirrors are often found in the hallways of various buildings (commonly known as "hallway safety mirrors"), including hospitals, hotels, schools, stores, and apartment buildings. They are usually mounted on a wall or ceiling where hallways intersect each other, or where they make sharp turns. They are useful for people to look at any obstruction they will face on the next hallway or after the next turn. They are also used on roads, driveways, and alleys to provide safety for road users where there is a lack of visibility, especially at curves and turns.[2]

The 10x or 20x medium power objective delivers comfortable viewing magnification and reasonably high resolution to see some finer details in the context of the larger specimen structure. It is commonly used for routine examination, counting cells, measuring proportions, and making sketches.

The mirrors are called "converging mirrors" because they tend to collect light that falls on them, refocusing parallel incoming rays toward a focus. This is because the light is reflected at different angles at different spots on the mirror as the normal to the mirror surface differs at each spot.

A curved mirror is a mirror with a curved reflecting surface. The surface may be either convex (bulging outward) or concave (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices. The most common non-spherical type are parabolic reflectors, found in optical devices such as reflecting telescopes that need to image distant objects, since spherical mirror systems, like spherical lenses, suffer from spherical aberration. Distorting mirrors are used for entertainment. They have convex and concave regions that produce deliberately distorted images. They also provide highly magnified or highly diminished (smaller) images when the object is placed at certain distances.

The Gaussian mirror equation, also known as the mirror and lens equation, relates the object distance d o {\displaystyle d_{\mathrm {o} }} and image distance d i {\displaystyle d_{\mathrm {i} }} to the focal length f {\displaystyle f} :[2]

While the basic 3 objective arrangement still dominates today, some microscopes incorporate additional objectives or special enhancements for increased performance and capabilities.

Objective lens microscopefunction

The sign convention used here is that the focal length is positive for concave mirrors and negative for convex ones, and d o {\displaystyle d_{\mathrm {o} }} and d i {\displaystyle d_{\mathrm {i} }} are positive when the object and image are in front of the mirror, respectively. (They are positive when the object or image is real.)[2]

The lowest magnification objective is typically a 4x or 10x lens. Its primary purpose is to provide a wide field of view of the overall specimen on the slide for initial orientation and scanning. The low magnification reduces aberrations from optical imperfections.

For concave mirrors, whether the image is virtual or real depends on how large the object distance is compared to the focal length. If the 1 / f {\displaystyle 1/f} term is larger than the 1 / d o {\displaystyle 1/d_{\mathrm {o} }} term, then 1 / d i {\displaystyle 1/d_{\mathrm {i} }} is positive and the image is real. Otherwise, the term is negative and the image is virtual. Again, this validates the behavior described above.

A collimated (parallel) beam of light diverges (spreads out) after reflection from a convex mirror, since the normal to the surface differs at each spot on the mirror.

Higher magnification requires higher resolution to realize the full benefit. The higher-powered objectives have correspondingly greater resolving power to take advantage of the increased magnification whereas the lower-power lenses have comparatively less resolution which is ample for their magnification level.

Lenses with lower power and larger fields of view can have optics optimized for brightness whereas high magnification lenses with narrow fields are optimized for resolution at the expense of brightness.

A convex mirror or diverging mirror is a curved mirror in which the reflective surface bulges towards the light source.[1] Convex mirrors reflect light outwards, therefore they are not used to focus light. Such mirrors always form a virtual image, since the focal point (F) and the centre of curvature (2F) are both imaginary points "inside" the mirror, that cannot be reached. As a result, images formed by these mirrors cannot be projected on a screen, since the image is inside the mirror. The image is smaller than the object, but gets larger as the object approaches the mirror.

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Microscopeparts

What is the objective lens of a microscopeexplain

Practically, low magnification facilitates efficient scanning of the overall specimen to find areas of interest to study further, saving significant time compared to searching blindly at high power. It provides necessary contextual orientation.

The multiple objectives with parcentered optics allow users to quickly switch between lenses and magnifications to obtain just the right view. This facilitates efficient and intuitive workflows.

The mathematical treatment is done under the paraxial approximation, meaning that under the first approximation a spherical mirror is a parabolic reflector. The ray matrix of a concave spherical mirror is shown here. The C {\displaystyle C} element of the matrix is − 1 f {\displaystyle -{\frac {1}{f}}} , where f {\displaystyle f} is the focal point of the optical device.

Round convex mirrors called Oeil de Sorcière (French for "sorcerer's eye") were a popular luxury item from the 15th century onwards, shown in many depictions of interiors from that time.[3] With 15th century technology, it was easier to make a regular curved mirror (from blown glass) than a perfectly flat one. They were also known as "bankers' eyes" due to the fact that their wide field of vision was useful for security. Famous examples in art include the Arnolfini Portrait by Jan van Eyck and the left wing of the Werl Altarpiece by Robert Campin.[4]

Typesof objectivelenses

The set of 3 objective lenses on most compound microscopes elegantly fulfills the range of observational needs in microscopy, from scanning the big picture to examining the most minute details. Their differing optical properties and fields of view provide efficient and flexible viewing capabilities not possible with a single objective lens. The specific numbers and powers may be tailored for particular applications, but the core triad arrangement remains ubiquitous out of logical necessity.

The provision of 3 objective lenses with differing optical properties confers important complementary advantages that enhance the microscopy user experience and workflow efficiency.

The major components of a compound microscope are the ocular lens in the eyepiece, the objective turret housing multiple objective lenses, the condenser lens below the stage, the illumination system, and the mechanical arm. Each part plays a critical optical or functional role.

A concave mirror, or converging mirror, has a reflecting surface that is recessed inward (away from the incident light). Concave mirrors reflect light inward to one focal point. They are used to focus light. Unlike convex mirrors, concave mirrors show different image types depending on the distance between the object and the mirror.

The image location and size can also be found by graphical ray tracing, as illustrated in the figures above. A ray drawn from the top of the object to the mirror surface vertex (where the optical axis meets the mirror) will form an angle with the optical axis. The reflected ray has the same angle to the axis, but on the opposite side (See Specular reflection).

Proper illumination from below is vital for viewing clarity. The maximum resolution or resolving power is limited by the wavelength of light and optics. Higher quality objectives provide greater usable resolution to see fine details.

A question commonly asked about compound microscopes is: What’s the purpose of having 3 objective lenses attached to it? The answer is quite simple.

The range of magnifications enables users to choose the appropriate level for their particular application, whether surveying tissue architecture or examining subcellular organelles. No single objective lens can provide optimal performance across this wide range of viewing needs.

Phase contrast and fluorescence microscopy require specialized objectives with matched condenser optics to image transparent specimens. These are often incorporated as a fourth objective or replace one of the standard ones.