RBSE Class 12 Physics Chapter 12 — Atoms: Most Repeated Questions (2013–2026)

For an electron's wave to be stable (a standing wave) in its circular orbit, the circumference ( 2πr ) must contain an integer number ( n ) of de Broglie wavelengths ( λ ):

Standing Wave Condition: 2πr=nλ

De Broglie Wavelength:

λ=h/p=h/mv

2πr=n(h/mv)

Angular Momentum ( L=mvr ):

mvr=nh/2π

L=nh/2π

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Bohr's model has two major limitations:

​ Atomic stability: an orbiting electron, being an accelerating charge, should continuously radiate energy and spiral into the nucleus almost instantly — contradicting the observed stability of atoms

Atomic spectra: this predicted a continuous spectrum, but atoms actually emit light only at specific wavelengths (discrete line spectra), which Rutherford's model could not explain

External Field Effects: It failed to explain the splitting of spectral lines when atoms were subjected to external fields (the Zeeman effect in a magnetic field and the Stark effect in an electric field)

​

All solved questions for this chapter are in the full RBSE Physics PYQ book.

1.Bohr’s model could explain the spectrum of hydrogen and hydrogen-like atoms only, but not the spectra of multi-electron atoms

2. It could not explain the splitting of spectral lines in the presence of magnetic and electric fields

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Kinetic Energy =K = -E

=-(-13.6eV)

=+13.6eV

Potential energy=2E

=2×-13.6eV

=-27.2eV

All solved questions for this chapter are in the full RBSE Physics PYQ book.

F_c=F_q

mv²/γ=kq₁q₂/γ²

mv²/γ=kZe(e)/γ²

mv²=kZe²/γ (1)

Bohr's second postulate (quantization of angular momentum, L ):

L=mvγ=nh/2π

v=nh/2πmγ

K=-E

E=-XeV

K=-(-XeV)

K=+XeV

All solved questions for this chapter are in the full RBSE Physics PYQ book.