A astronomical telescope has objective and eye-piece of focal lengths 40 cm, 4 cm, respectively. To view an object 200 cm away from the objective, the lenses must be seperated by a distance
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A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power […]
The frequency of a light wave in a material is 2 x 10¹⁴ Hz and wavelength is 5000Å. The refractive index of material will be
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(a) 1.5 (b) 3 (c) 1.33 (d) […]
A radioactive nucleus of mass M emits a photon of frequency v and the nucleus recoils. The recoil energy will be
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(a) Mc² – hv (b) h²v² / 2Mc² (c) zero (d) […]
The radioactivity of a certain material drops to 1/16 of the initial value in 2 hours. The half-life of this radio nuclide is
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(a) 10 min (b) 20 min (c) 30 min (d) […]
Which one of the following statements is true, if half-life of a radioactive substance is 1 month?
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(a) 7/8th part of the substance will disintegrate in 3 months (b) 1/8th part of […]
₉₂U²³⁵ undergoes successive disintegrations with the end product of ₈₂P²⁰³. The number of α and β-particles emitted are
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(a) α=8,β=6 (b) α=3,β=3 (c) α=6,β=4 (d) α=6,β=0
Correct Answer:
α=8,β=6
Explanation:
₉₂U²³⁵ → end […]
A radioactive sample S₁ having an activity of 5 μCi has twice the number of nuclei as another sample S₂ which has an activity of 10 μCi. The half lives of S₁ and S₂ can […]
The half-life period of a radio-active element X is same as the mean life time of another radio-active element Y. Initially they have the same number of atoms. Then
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(a) X and […]
In gamma ray emission from a nucleus
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(a) only the proton number changes (b) both the neutron number and the proton number change (c) there is no change in the proton number […]
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