convex (converging) lens?...?

Question

1. give examples of optical instruments that uses a convex or converging lens?
2. how do lenses change the direction of light rays and form images?

Answer 1

1. Microscope, telescope, camera, reading glasses (& many others).
2. Lenses work by refraction. See the ref.

Answer 2

The answer depends on the emphasis when the question was asked: a) why does A convex lens converge light rays? b) why does a CONVEX lens converge light rays? c) why does a convex LENS converge light rays? d) why does a convex lens CONVERGE light rays? e) why does a convex lens converge LIGHT rays? f) why does a convex lens converge light RAYS? Answers: a) why does A convex lens converge light rays? Because just one lens can have sufficient refracting power to do it. In fact, just one surface of one lens is sufficient, e.g. a plano-convex lens. b) why does a CONVEX lens converge light rays? Because to make a beam of parallel rays converge, the outer rays must be refracted through greater angles than the inner rays. At the center of a convex lens, the front and rear surfaces are parallel - they do not refract a perpendicular ray at all. Near the edges, the angle between the front and rear surfaces is at a maximum so, like a prism, the rays of light are refracted away from the apex of the prism converging to where they will eventually intersect central rays. At intermediate distances from the center of the lens, the rays need to be refracted by progressively smaller amount to converge at the same intersection (i.e. the focal point) so the angles between the front and rear surfaces are progressively smaller. Spherical lens surfaces provide just the right amount of angular variation. The spherical surfaces must be convex, i.e. not concave, or the angles would vary in the wrong directions. c) why does a convex LENS converge light rays? In physics, a lens is defined as an object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons, etc. If we didn't have a lens, we wouldn't be doing physics :) d) why does a convex lens CONVERGE light rays? Because, as discussed above, it is shaped just right to get each ray to go to the right place, and also, it is made of a suitable material, such as transparent plastic or glass. e) why does a convex lens converge LIGHT rays? Good question! Because plastic and glass are transparent to light, but they have another property known as a "refractive index" which measures the amount by which light slows down when it enters them. This is the key to the bending of light that occurs, and is also applied in other forms of energy focusing, such as sound and radio waves. f) why does a convex lens converge light RAYS? Rays are a convenient way of tracking the path of light through a lens.

Answer 3

1.Telescopes ,Microscope
2.Normal carefulness and unusual carefulness

Normal carefulness on Telescopes
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In This time the reflection will be create in termination

Unusual carefulness
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In this time the reflection will be create in 25cm from your eye