Sail through JEE 2020: Atoms and Nuclei

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Question 1

The half life of a radioactive substance is 20 minutes. The time taken between 50% decay and 87.5% decay of the substance will be

• A40 minutes
• B10 minutes
• C30 minutes
• D25 minutes

Question 2

The ratio of volume occupied by an atom to the volume of the nucleus is

• A10⁵.1
• B10²⁰.1
• C10¹⁵-1
• D1:10¹⁵

Question 3

When a hydrogen atom is raised from ground energy level to excited energy level, then

• Apotential energy increases and kinetic energy decreases
• Bkinetic energy increases and potential energy decreases
• CBoth KE and PE increase
• DBoth KE and PE decrease

Question 4

The half life of -decay of uranium ₉₂U²²⁸ is 4.47×10⁸ yr. If a rock contains 60% of original ₉₂U²²⁸ atoms, then its age is
[take log6 = 0.778, log 2 = 0.3]

• A1.2 × 10⁷ yr
• B3.3 × 10⁸ yr
• C4.2 × 10⁹ yr
• D6.5 × 10⁹ yr

Question 5

When the momentum of a photon is changed by an amount p’ then the corresponding change in the de-Broglie wavelength is found to be 0.20%. The, the original momentum of then photon was

• A300 p’
• B500 p’
• C400 p’
• D100 p’

Question 6

The de Broglie wavelength of an electron (mass = 1 × 10^-30 kg, charge = 1.6 × 10^-19 C) with a kinetic energy of 200 eV is (Planck’s constant = 6.6 × 10^-34J_s)

• A9.60 × 10-11 m
• B8.25 × 10-11 m
• C6.25 × 10-11 m
• D5.00 × 10^-11 m

Question 7

In an inelastic collision an electron excites as hydrogen atom from its ground state to a M-shell state. A second electron collides instantaneously with the excited hydrogen atom in the M-state and ionizes it. At least how much energy the second electron transfers to the atom in the M-state?

• A+3.7 eV
• B+1.51 eV
• C-3.4 eV
• D-1.51 eV

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