Terms for Lenses
Terms for Lenses
The lenses are made of two curved surfaces which are a part of the sphere. The diagram below shows important terms related to Convex Lens.
The diagram below shows important terms related to Concave Lens.
Optical Centre (O):
The central point O of the lens is called its optical centre. A ray incident towards the optical centre passes almost without any deviation through the lens.
Centres of Curvature:
The centres of the two imaginary spheres of which the lens is a part are called centre of curvature of the lens. It represented by . A lens has two centres of curvature with respect to its two curved surfaces.
Radii of Curvature:
The radii of the two imaginary spheres of which the lens is a part are called radii of curvature of the lens. A lens has two radii of curvature. These may or may not be equal.
Principal Axis:
Lens is bounded by two spherical surfaces, and therefore, has two centres of curvature and
. The imaginary line joining them is called the Principal Axis of the lens.It passes through the optical centre.
Principal Focus
A lens has two surfaces and hence two focal points first focal point is an object on the principal axis foe which image is at infinity while second focal point is an image point on the principal axis for which object is at infinity.
First Principal Focus It is a point on the principal axis of lens, the rays starting from or directed to which become parallel to principal axis after refraction.
Second Principal Focus It is the point on the principal axis at which the rays coming parallel to the principal axis converge on the other side of lens (convex) or appear to meet on the same side of lens (concave) after refraction from the lens.
Both the foci of convex lens are real while that of concave lens are virtual.
Focal Length:
The distance between optical centre of a lens and the point where the parallel beam of light converge or appear to diverge from i.e. focus is called focal length.
Focal Plane:
The plane passing through the focus and perpendicular to the principal axis is called focal plane.
Aperture :
The effective diameter of its light transmitting area is called the aperture of lens. It controls the brightness i.e. intensity of image formed by a lens which depends on the light passing through the lens. It is proportional to the square of aperture.i.e.
The centers of the two imaginary spheres of which the lens is a part are called _______________________ . | |||
| Right Option : A | |||
| View Explanation | |||
For a lens there is/are _____________ centres of curvature. | |||
| Right Option : B | |||
| View Explanation | |||
Which of the following are correct ? (a) The centres of the two imaginary spheres of which the lens is a part are called centre of curvature of the lens. (b) The radii of the two imaginary spheres of which the lens is a part are called radii of curvature of the lens. | |||
| Right Option : C | |||
| View Explanation | |||
Students / Parents Reviews [10]
Abhyas is a complete education Institute. Here extreme care is taken by teacher with the help of regular exam. Extra classes also conducted by the institute, if the student is weak.
Om Umang
10thA marvelous experience with Abhyas. I am glad to share that my ward has achieved more than enough at the Ambala ABHYAS centre. Years have passed on and more and more he has gained. May the centre flourish and develop day by day by the grace of God.
Archit Segal
7thMy experience with Abhyas is very good. I have learnt many things here like vedic maths and reasoning also. Teachers here first take our doubts and then there are assignments to verify our weak points.
Shivam Rana
7thIt has a great methodology. Students here can get analysis to their test quickly.We can learn easily through PPTs and the testing methods are good. We know that where we have to practice
Barkha Arora
10thAbhyas Methodology is very good. It is based on according to student and each child manages accordingly to its properly. Methodology has improved the abilities of students to shine them in future.
Manish Kumar
10thOne of the best institutes to develope a child interest in studies.Provides SST and English knowledge also unlike other institutes. Teachers are co operative and friendly online tests andPPT develope practical knowledge also.
Aman Kumar Shrivastava
10thMy experience was very good with Abhyas academy. I am studying here from 6th class and I am satisfied by its results in my life. I improved a lot here ahead of school syllabus.
Ayan Ghosh
8thIt was a good experience with Abhyas Academy. I even faced problems in starting but slowly and steadily overcomed. Especially reasoning classes helped me a lot.
Cheshta
10thIt was good as the experience because as we had come here we had been improved in a such envirnment created here.Extra is taught which is beneficial for future.
Eshan Arora
8thAbout Abhyas metholodology the teachers are very nice and hardworking toward students.The Centre Head Mrs Anu Sethi is also a brilliant teacher.Abhyas has taught me how to overcome problems and has always taken my doubts and suppoeted me.
