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In Academic Year (2021–2022) Central Board of Secondary Education (CBSE) Announced That Board Examinations of Class 10th and 12th will be conducted in two terms, the first term in November–December 2021 and second term in April–March 2022. In 2023, the class 12 Board Exam was conducted between 15 February and 5 April, and the results were ...
The 2025 CBSE board examination for Class 10 were held from 15 February till 18 March and from 15 February till 4 April for class 12. The usual starting time for each exam was 10:30 am( IST ) but depending on the length and/or maximum marks for the subject, the finishing time was either 12:30 pm ( IST ) (2 hours, shorter exams, usually 40-50 ...
On 12 April 2018, the police said that Rakesh Kumar, who leaked the class 12 economics paper, had leaked class 10 mathematics paper also. [40] Consequently, the Central Board of Secondary Education has put in place a system of "encrypted" question papers, which are supposed to be printed by the schools half an hour before the exam starts. [41]
A burning apparatus consisting of two biconvex lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
The early writers discussed here treated vision more as a geometrical than as a physical, physiological, or psychological problem. The first known author of a treatise on geometrical optics was the geometer Euclid (c. 325 BC–265 BC).
Geometrical optics, or ray optics, is a model of optics that describes light propagation in terms of rays.The ray in geometrical optics is an abstraction useful for approximating the paths along which light propagates under certain circumstances.
Vision of humans and other organisms depends on several organs such as the lens of the eye, and any vision correcting devices, which use optics to focus the image. The eyes of many animals contains a lens that focuses the light of its surroundings onto the retina of the eye. This lens is essential to producing clear images within the eye.
[23] [24] The upper end of the range is given in terms of normal visual performance as 10 8 cd/m 2 (100,000,000 or one hundred million candelas per square meter). [25] Dilation and constriction of the pupil. The eye includes a lens similar to lenses found in optical instruments such as cameras and the same physics principles can be applied.