Assertion: In a metal all the free electrons have same energy.

Reason: : Electrons do not obey Pauli's Exclusion principle

• 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 and reason is false

• If both assertion and reason are false

The ground state energy of hydrogen atom is -13.6 eV. What is the potential energy of the electron in the state?

• 0 eV

• -27.2 eV

• 1 eV

• 2 eV

Energy required to break one bond in DNA is approximately

• ∼ 1 eV

• ∼ 0.1 eV

• ∼ 0.01 eV

• ∼ 2.1 eV

Assertion: Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate. 

Reason:  According to classical physics all moving electrons radiate.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

Maximum energy is evolved during which of the following transitions?

• n = 1 to n= 2

• n = 2 to n= 6

• n = 2 to n= 1

• n = 6 to n= 2

If λ₁ and λ₂ are the wavelengths of the first members of the Lyman and Paschen series respectively, then λ₁ : λ₂ is

• 1 : 3

• 1 : 30

• 7 : 50

• 7 : 108

Electrons in a certain energy level n = n₁ can emit 3 spectral lines. When they are in another energy level, n=n₂ they can emit 6 spectral lines. The orbital speed of the electrons in the orbits are in the ratio

• 4 : 3

• 3 : 4

• 2 : 1

• 1 : 2

The ground state energy of H-atom is 13.6 eV. The energy needed to ionize H-atom from its second excited state is

• 1.51 eV

• 3.4 eV

• 13.6 eV

• 12.1 eV

Continuous emission spectrum, emitted wavelength about spectrum, the range depends upon:

• temperature of the source

• material of the source

• surface area of the source

• all of the above

160.

If the temperature of a black body is doubled, the wavelength at which the spectral radiancy has its maximum, is 

• doubled

• halved

• quadrupled

• unchanged