A short-sighted person cannot see objects situated beyond 2m from him distinctly. What should be the power of the lens which he should use for seeing distant objects clearly ?
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Which of the following is noth the number of ways of selecting `n` objects from `2n` objects of which `n` objects are identical
Correct Answer - D `(d)` We can take `0` indentical and `n` distinct , `1` identical and `n-1` distinct , `2` identical and `n-2` distinct and so on… `:.` Total no....
2 Answers 1 views
A student with defective eye-sight cannot see clearly anything that is father from his eyes than 50 cm. What kind of lens would enable him to see dist
Correct Answer - Concave lens, power =`-2D`
2 Answers 1 views
A person can see objects as near as 40 cm and as far as 3 m. What kind of spectacles will be required (a) for reading purposes, (b) for seeing distant
Correct Answer - (a) `1.5`D(convex), (b) `0.33`D(concave), with reading glasses he can see clearly from 25 cm to `54.5` cn and with distant glasses from 46 cm to infinity
2 Answers 1 views
Two men, one far-sighted and one short-sighted one, see objects through their spectacles of his short-sighted friend, he found that he could see disti
Correct Answer - `12.5`cm
2 Answers 1 views
Calculate the focal length of a convex lens of crown glass of dispersive power 0.012 and concave lens of dispersive power 0.020 that from an achromati
Correct Answer - `r_("common")=1.11 m,0.644m`
2 Answers 2 views
A convex lens of crown glass is perfectly cemented to a plano-concave lens of flint glass to form an achromatic combination of power `div 5D`. Calcula
Correct Answer - `8.6cm, 12 cm`
2 Answers 2 views
ln a biprism experiment, 21 fringes are seen distinctly on a screen at a distance 1 m, when the sources are 0.5 mm apart. What is the coherent length
Correct Answer - `2 xx 10^(-4)s`
2 Answers 1 views
Find the focal length and power of a convex lens, which when placed in contact with a concave lens of focal length `25 cm` forms a real image `5` time
Correct Answer - 10 cm, 10D
2 Answers 1 views
A student uses spectacles of number -2 for seeing distant objects. Commonly used lenses for her/his spectacles are
Correct answer is (A) bi-concave
2 Answers 4 views
In which of the case, a man wearing glasses of focal length, \( +1 m \) cannot clearly see beyond \( 1 m \).
Answer: in each of these cases The man is wearing glasses of positive power (converging lens). Hence, he cannot see nearby objects clearly. In other words, he is farsighted. Since he...
2 Answers 1 views