Structure of Atom

Assertion : Water is used as a moderator in nuclear reactor.

Reason : Moderator is a light substance that absorb neutrons.

• If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

• If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

• If Assertion is true but Reason is false.

• If Assertion is false but Reason is true.

Assertion : Ionisation potential of B (atomic no.5) is less than Be (atomic no. 4).

Reason : The first electron released from Be is of p-orbital but that from B is of s-orbital.

• If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

• If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

• If Assertion is true but Reason is false.

• If Assertion is false but Reason is true.

The emission spectrum of hydrogen discovered first and the region of the electromagnetic spectrum in which it belongs, respectively are

• Lyman, ultraviolet

• Lyman, visible

• Balmer, ultraviolet

• Balmer, visible

As per de-Broglie's formula a macroscopic particle of mass 100 g and moving at a velocity of 100 cm s^-1 will have a wavelength of

• 6.6 × 10^-29 cm

• 6.6 × 10^-30 cm

• 6.6 × 10^-31 cm

• 6.6 × 10^-32 cm

Assertion: For Balmer series of hydrogen spectrum, the value n₁ = 2 and n₂ = 3, 4, 5.
Reason: The value of n for a Line in Balmer series of hydrogen spectrum having the highest wavelength is 4 and 6.

• If both assertion and reason are true and reason is a correct explanation of the assertion.

• If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both the assertion and reason are false.

Assertion: Absolute values of the internal energy of substances can not be determined.
Reason: It is impossible to determine the exact values of constituent energies of the substances.

• If both assertion and reason are true and reason is a correct explanation of the assertion.

• If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both the assertion and reason are false.

Assertion: The absorption spectrum consists of some bright lines separated by dark spaces.
Reason: Emission spectrum consists of dark lines.

• If both assertion and reason are true and reason is a correct explanation of the assertion.

• If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both the assertion and reason are false.

₁₁Na²⁴ 1s radioactive and it decays to:

• ₉F²⁰ and $\mathrm{\alpha }$-particles

• ₁₃Al²⁴ and positron

• ₁₁Na²³ and neutron

• ₁₂Mg²⁴ and $\mathrm{\beta }$-particles

Which of the following does not represent the mathematical expression for the Heisenberg uncertainty principle?

• $∆$x ^.$∆$p $⩾$ h/(4$\mathrm{\pi }$)

• $∆$x ^. $∆v$ $⩾$ h/(4$\mathrm{\pi m}$)

• $∆E$ ^. $∆t$ $⩾$ h/(4$\mathrm{\pi }$)

• $∆E$ ^. $∆x$ $⩾$ h/(4$\mathrm{\pi }$)

During the emission of a positron from a nucleus, the mass number of the daughter element remains the same but the atomic number

• is decreased by 1 unit

• is decreased by 2 units·

• is increased by 1 unit

• remains unchanged