The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are:
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(a) […]
The magnifying power of the astronomical telescope for normal adjustment is 50. The focal length of the eyepiece is 2 cm. The rquired length of the telescope for normal adjustment is
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(a) […]
A small angled prism of refractive index 1.4 is combined with another small angled prism of refractive index 1.6 to produce dispersion without deviation. If the angle of first prism is 6⁰, then the angle […]
When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts a plane sheet of glass. This implies that the liquid must have refractive index
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(a) […]
The distance of the moon form the earth is 3.8×10⁵ km. Supposing that the eye is most sensitive to the light of wavelength 550 nm, the seperation of two points on the moon that can […]
A person has a minimum distance of distinct vision as 50 cm. The power of lenses required to read a book at a distance of 25 cm is
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(a) 3 D (b) […]
A thin prism of angle 15⁰ made of glass of refractive index µ₁ = 1.5 is combined with another prism of glass of refractive index µ₂ = 1.75. The combination of the prism produces dispersion […]
When an object is placed 40cm from a diverging lens, its virtual image is formed 20 cm from the lens. The focal length and power of lens are
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(a) F=-20 cm, P=-5 D […]
Which one of the following is not due to total internal reflection?
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(a) working of optical fibre (b) Difference between apparent and real depth of pond (c) Mirage on hot summer days […]
An object is 8 cm high. It is desired to form a real image 4 cm high at 60 cm from the mirror. The type of mirror needed with the focal length is
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