671.

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

β- emission is always accompained by

• formation of antineutrino and α-particle

• emission of α-particle and γ-ray

• formation of antineutrino and γ-ray

• formation of antineutrino and positron

The value of Planck's constant is 6.63 x 10^-34 Js. The speed of light is 3 x 10¹⁷ nms^-1. Which value is closest to the wavelength in nanometer of a quantum of light with frequency of 6 x 10¹⁵ s^-1?

• 10

• 25

• 50

• 75

What is the maximum numbers of electrons that can be associated with the following set of quantum numbers? n = 3, l = 1 and m =-1.

• 10

• 6

• 4

• 2

An atomic nucleus having low n/p ratio tries to find stability by

• the emission of an α-particle

• the emission of a positron

• capturing an orbital electron (K-electron capture)

• emission of β -particle

(₃₂Ge⁷⁶, ₃₄Se⁷⁶) and (₁₄Si³⁰, ₁₆S³²) are examples of

• isotopes and isobars

• isobars and isotones

• isotones and isotopes

• isobars and isotopes

₉₈Cf²⁴⁶ was formed along with a neutron when an unknown radioactive substance was bomabrded with ₆C¹². The unknown substance is

• ₉₁Pa²³⁴

• ₉₀Th²³⁴

• ₉₂U²³⁵

• ₉₂U²³⁸