PREPWISER.
Practise online

Atomic Physics formula sheet

Every formula in the Atomic Physics chapter for JEE Main, with one line on when it applies. Topic 1 is open to everyone; sign in free to read all 18 and download the PDF.

Sign in to read all 18Download PDF

Read the first part free. Sign in free with Google to read the rest and download the PDF: 2 A4 pages.2 A4 pages, ready to print.

How we count: 7× asked means 7 past JEE Main questions in the PrepWiser bank needed that formula, and "last" is the latest year one appeared. ★ marks formulas asked 8 or more times.

Atom models and α-scattering

α-scattering
3× asked, last 2026
N(θ)∝1sin⁡4(θ/2)N(\theta)\propto\frac1{\sin^4(\theta/2)}
Most pass straight; ~1 in 8000 turn back beyond 90∘90^\circ. Nucleus ~10−1410^{-14} m, atom ~10−1010^{-10} m.
Distance of closest approach
3× asked, last 2026
r0=14πε0 2Ze2Kr_0=\frac1{4\pi\varepsilon_0}\,\frac{2Ze^2}K
Head-on α of KE KK; r0∝Z/Kr_0\propto Z/K. With KK in eV: r0=9×109⋅2Z⋅1.6×10−19/Kr_0=9\times10^9\cdot2Z\cdot1.6\times10^{-19}/K.
Impact parameter
2× asked, last 2026
b=14πε0 Ze2Kcot⁡θ2b=\frac1{4\pi\varepsilon_0}\,\frac{Ze^2}K\cot\frac\theta2
Smaller bb, larger θ\theta; b=0b=0 is head-on.

Practise Atomic Physics questions as you read. Free, and you can start without signing up.

Practise Atomic Physics

15 more formulas in 4 topics

Bohr's model and hydrogen-like ions; Scaling with n and Z; Excitation, ionisation and line count; and Hydrogen spectrum. Read the first part free. Sign in free with Google to read the rest and download the PDF.

Sign in to read the restYou come straight back to this spot.Download the PDF

Bohr's model and hydrogen-like ions

  • Bohr's postulates12×
  • Orbit radius9×
  • Orbit speed4×
  • Energy levels15×
  • Matching levels across ions11×

Scaling with n and Z

  • Scaling (one-electron ions)12×
  • Orbital current, field, moment4×
  • Bohr's rule for other forces3×

Excitation, ionisation and line count

  • Excitation and ionisation13×
  • Number of spectral lines6×

Hydrogen spectrum

  • Rydberg formula16×
  • Spectral series4×
  • Longest and shortest line11×
  • Ratios between lines17×
  • Recoil of the atom3×

Practise Atomic Physics next

About 105 past JEE Main questions from this chapter, with instant answer checking and step-by-step solutions where available. Free, and you can start without signing up.

Practise Atomic Physics

Also free on PrepWiser

Spotted a mistake? Write to support@prepwiser.in and we will fix it in the next version.

Version 1, October 2026. Free to share for study, as it is. Please don't sell it or remove the PrepWiser name.

PractiseSign in to read all 18Download PDF
Free with Google, takes a few seconds2 pages, free