Definition
Report | Achu asks : A middle aged woman wears eye glasses with power of -5.5D for myopia. Her doctor prescribed a correction of +1.5D in the near vision portion of her bifocals.This is measured relative to the main part of the lens. (1)What is the focal length of her distant viewing portion of the lens? (2)What is the focal length of the near viewing portion of the lens? |
Report | Ranjita asks : An astronmical telescope has an objective of focal length 200 cm and an eyepiece of focal length 10 cm . An observer ajusts the distance of the eyepiece from the objective to obtain the image of the sun on a screen 40 cm behind the eyepiece. The diameter of the sun’s image is 6.0 cm .Find the diameter of the sun. The average earth-sun distance is 1.5x 1011 m. |
Report | Debi kalyan satpathy asks : The dispersive power of the materials of two lenses are in the ratio 4/3.If the achromatic combination of the two lenses has focallength of +60cm,the focal length of component lense is:- |
Report | Pratyush srivastava asks : If the focal length of a lens of a camera is 5f and that of another is 2.5f. What is the time of exposure for the second, if for the first one is 1/200 s? |
Report | Divesh kukreja asks : The sun subtends an angle A radian at the pole of a concave mirror of focal length f. the diameter of the image of sun formed by mirror is |
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