Origin Of Quantum Mechanics MCQ Level - 2 - IIT JAM MCQ

Number of electrons in n^th orbit is given by 2n²
∴  total electrons is = 2(1)² + 2(2²)
= 2 + 8 = 10
The correct answer is: 10

Transition to n=1 and n=2 are refered to as Lyman and Balmer series.

For Lyman Series wavelength will be longest when energy the electron has transition from n=2 to n=1 level.
For Balmer  Series wavelength will be longest when  energy the electron has transition from n=3 to n=2 level.

de-Broglie wave length, λ = h/p, where h is the Planck's constant.

The correct answer is: Planck’s constant

Correct Answer :- a

Explanation : White light does not produce any photoelectric effect because the range of wavelength in white light is (400 – 700)nm. The energy corresponding to this range of wavelength is small in comparison to the work function of any metal in general.

The correct answer is: No photo-current observed.

The reduced mass of positronium is

In the case of hydrogen atom, for simplification we take the reduced mass of the electron and proton system to be m_e.

So, the only difference between the hydrogen and positronium atom is that the positronium atom has the energy levels half of the hydrogen atom.


= 6.0 eV
The correct answer is: 6.0 eV

Consider He⁺ which is a hydrogen like atom. We can apply the Bohr theory to see that energy required to go from

What we need is 
Given is the total energy required to get He²⁺ from He.

We cannot apply Bohr theory directly to Helium because it is not a hydrogen like atom.

The correct answer is: 24.6 eV

In the initial case (free particle)
V = 0
Total energy = E = kinetic energy
Since the total energy remains conserved
∴ E = K.E_new + V
K.E. (new) = E – V
Now, new wavelength = 

If V_s is the stopping potential then

Compare it with y = mx + c (equation of a straight time)

c = intercept on y-axis

The correct answer is: h/e

Energy radiated from a black body is proportional to the 4th power of its absolute temp is

E_new = 16E

Heat required to melt ice of mass m is proportional to the mass.

So, now the mass of ice that can be melted will 16 times the previous mass of ice melted.

The correct answer is: 16

In case the electron is replaced by the muon, we will have to consider the reduced mass of the proton- muon system.

The Rydberg constant is changed by a factor of.

The Rydbergs constant is proportional to the reduced mass of the system in consideration.

R₁ = Rydbergs constant for e^– and p system is proportional to reduced mass of e^– and p

R₂ = Rydbergs constant for µ and p system

∴  New energy levels are