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Telephoto lenses using diffractive elements to minimize chromatic aberration are commercially available from Canon and Nikon for interchangeable-lens cameras; these include 800mm f/6.3, 500mm f/5.6, and 300mm f/4 models by Nikon (branded as "phase fresnel" or PF), and 800mm f/11, 600mm f/11, and 400mm f/4 models by Canon (branded as ...
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 ...
All India Secondary School Examination, commonly known as the class 10th board exam, is a centralized public examination that students in schools affiliated with the Central Board of Secondary Education, primarily in India but also in other Indian-patterned schools affiliated to the CBSE across the world, taken at the end of class 10. The board ...
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.
A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. [1] The term is also used to refer to other lenses that provide a negative index of refraction. [2] Flat lenses require a refractive index close to −1 over a broad angular range.
The results of the examinations are usually declared in the first week of May to mid-June. In general, about 80% of candidates receive a passing score. [8] The Delhi High Court has directed the Central Board of Secondary Education and Delhi University to discuss the ways by which the results of the main exam, revaluation, and compartment exam can be declared earlier than usual so that ...
A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x). The lens focuses light in the same way as a conventional lens. If the refractive index of a medium is not constant but varies gradually with the position, the material is known as a gradient-index (GRIN) medium and is described by gradient index ...
The bottom example depicts a real lens with spherical surfaces, which produces spherical aberration: The different rays do not meet after the lens in one focal point. The further the rays are from the optical axis, the closer to the lens they intersect the optical axis (positive spherical aberration). (Drawing is exaggerated.)