Physics, asked by rajeshwar6, 1 year ago

collect information about the lenses available in optical shop and find out focal length of the lens may be determined by the given power of lens and write a report on it

Answers

Answered by mynameissamarth

Concave lenses

A concave lens is exactly the opposite with the outer surfaces curving inward, so it makes parallel light rays curve outward or diverge. That's why concave lenses are sometimes called diverging lenses. (One easy way to remember the difference between concave and convex lenses is to think of concave lenses caving inwards.)

Photo: A concave lens makes parallel light rays diverge (spread out) so that they appear to come from a point behind the lens—the focal point. The distance from the center of the lens to the focal point is, again, the focal length of the lens. However, in this case, since the light rays don't really come from here, we call it a virtual focal point.

Concave lenses are used in things like TV projectors to make light rays spread out into the distance. In a flashlight, it's easier to do this job with a mirror, which usually weighs much less than a lens and is cheaper to manufacture as well.

Compound lenses

It's possible to make lenses that behave in more complex ways by combining convex and concave lenses. A lens that uses two or more simpler lenses in this way is called a compound lens.

How do you measure the power of a lens?

If you've ever looked through binoculars, a telescope, or a magnifying glass, you'll know that some lenses magnify (or reduce) the apparent size of an object much more than others. There's a simple measurement that tells you how powerful a lens is and it's known as the focal length. The focal length of a lens is the distance from the center of the lens to the point at which it focuses light rays. The shorter the focal length, the more powerful the lens. (It's easy to see why: an ordinary piece of glass would be like a lens of infinite focal length and wouldn't bring light rays to a focus at all. On the other hand, an infinitely powerful lens would bring lays rays to a focus in an infinitely short distance, with zero focal length. A real lens is somewhere between these two extremes.)

You'll find focal lengths written either in ordinary units of length (such as centimeters, millimeters, or inches) or in special optical units called diopters. The diopter measurement of a lens is the reciprocal of the focal length in meters (one divided by the focal length), so 1 diopter = 1 m, 2 diopters = 0.5 m, 3 diopters = 0.33 meters, and so on. Eyeglass prescriptions from opticians typically show the strength of the corrective lenses you need in diopters.

The focal length isn't the only important feature of a lens. Bigger lenses gather more light than smaller ones, so they make a brighter image. This is particularly important if you're choosing a lens for a camera, because the amount of light the lens gathers will determine what the image looks like. Camera lenses are usually rated with a measurement called the f-number, which is the focal length divided by the diameter. Generally speaking, lenses with a small f-number make brighter images. Lenses with a higher f-number have a bigger depth of focus: essentially, more of the object you're photographing and its surroundings are in focus at the same time. (If you want to know more, take a look at Louis Bloomfield's explanation of lens size.)

How are lenses made?

Photo: This magnifying glass uses a single convex lens made from plastic.

Until plastics became common in the 20th century, virtually all lenses were made by grinding solid pieces of glassinto different shapes. Convex lenses were made by using a concave-shaped grinding tool (and vice-versa), and then the roughly shaped lens was polished to make its final shape. The ordinary glass we use in windows and crockery isn't good enough to use for lenses, because it contains air bubbles and other imperfections. These cause light rays to divert from their correct path, making a fuzzy image or one that makes different colors of light behave in different ways (problems that optical scientists refer to as aberrations). Instead, lenses are made using a more refined material known as optical glass. For eyeglasses, many people now prefer plastic lenses because they're much lighter and safer than optical glass. Plastic lenses can be molded to shape, instead of being ground, so they can be made in huge quantities far more cheaply than glass lenses. Although ordinary plastic scratches easily, it can be coated with a thin layer of a protective material such as diamond-like carbon (DLC) to reduce the risk of damage. Some optical lenses are also coated with thin plastic to reduce annoying reflections; you can read how these anti-reflective coatings work in our article on thin-film interference.

Answered by chennaiah786

Answer:

SWAEROES ten commandments”

FEBRUARY 16, 2019~ MB

Malavath Poorna, star of the 2015 biopic Poorna: Courage Has No Limit, scaled Cerro Aconcagua in Argentina yesterday, to become the “world’s first tribal woman to scale [the] four highest mountain peaks located in four continents.”

Explanation:

At age 13, Poorna became the youngest woman ever to climb Sagarmatha (also known as Mt. Everest). Now 19, she credits her success to the “ten commandments” of the Social Welfare AEROES (or “SWAEROES”) movement, following B.R. Ambedkar’s ideas to educate and empower marginalized and scheduled caste children.The Swaeroes “ten commandments” are listed on the website of the Telangana Social Welfare Residential Educational Institutions Society

I am not inferior to anyone.

I am not inferior to anyone.I shall be the leader wherever I am.

I am not inferior to anyone.I shall be the leader wherever I am.I shall do what I love and be different.

I am not inferior to anyone.I shall be the leader wherever I am.I shall do what I love and be different.I shall always think Big and Aim high.

I am not inferior to anyone.I shall be the leader wherever I am.I shall do what I love and be different.I shall always think Big and Aim high.I shall be honest, hardworking and punctual.

I am not inferior to anyone.I shall be the leader wherever I am.I shall do what I love and be different.I shall always think Big and Aim high.I shall be honest, hardworking and punctual.I shall never blame others for my failures.I shall neither beg nor cheat.

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