(1). Number of nuclei of a radioactive substance at time t = 0 are 1000 and 900 at time t = 2 s. Then number of nuclei at time t = 4 s will be

• (a). 800
• (b). 790
• (c). 700
• (d). 810
• (e). None of these

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(2). A radioactive isotope has a half-life of 2 years. How long will it take the activity to reduce to 3% of its original value?

• (a). 4.8 years
• (b). 7 years
• (c). 10 years
• (d). 9.6 years
• (e). None of these

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(3). If the binding energy per nucleon of deuteron is 1.115 MeV, its mass defect in atomic mass unit is

• (a). 0.0048
• (b). 0.0024
• (c). 0.0012
• (d). 0.0006
• (e). None of these

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(4). An electron is moving in an orbit of a hydrogen atom from which there can be a maximum of six transitions. An electron is moving in an orbit of another hydrogen atom from which there can be a maximum of three transitions. The ratio of the velocity of the electron in these two orbits is

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(5). Suppose an electron is attracted towards the origin by a force k/r, where k is a constant and r is the distance of the electron from the origin. By applying Bohr model to this system, the radius of nth orbit of the electron is found to be rn and the kinetic energy of the electron is found to be Tn. Then which of the following is true?

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(6).

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(7).

• (a). A and C are isotopes
• (b). A and C are isobars
• (c). B and C are isotopes
• (d). A and B are isobars
• (e). None of these

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(8).

• (a). n = 3 to n = 1
• (b). n = 3 to n = 2
• (c). n = 4 to n = 2
• (d). n = 4 to n = 3
• (e). None of these

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(9). A radioactive nucleus (initial mass number A and atomic number Z) emits 3a-particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will be

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(10).

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(11).

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(12).

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(13).

• (a). 12 mm
• (b). 18 mm
• (c). 9 mm
• (d). 6 mm
• (e). None of these

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(14). A beam of beryllium nucleus (Z = 4) of kinetic energy 5.3 MeV is headed towards the nucleus of gold atom (Z = 79). What is the distance of closest approach?

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(15).

• (a). n = 1
• (b). n=2
• (c). n=3
• (d). n=4
• (e). None of these

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(16). A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 minutes, the rate becomes 1250 disintegrations per minute. Then, its decay constant (per minute) is

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(17). The set which represents the isotope, isobar and isotone respectively is

• (a). 1
• (b). 2
• (c). 3
• (d). 4
• (e). None of these

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(18).

• (a). 2 : 1
• (b). 1 : 2
• (c). 1 : 4
• (d). 4 : 1
• (e). None of these

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(19).

• (a). 1.33 MeV and 1.17 MeV in succession
• (b). 1.17 MeV and 1.33 MeV in succession
• (c). 1.37 MeV and 1.13 MeV in succession
• (d). 1.13 MeV and 1.37 MeV in succession
• (e). None of these

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(20).

• (a). 90, 233
• (b). 90, 238
• (c). 91, 234
• (d). 93, 238
• (e). None of these

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