A beam of \(5.0\times10^{5}\) α-particles falls on the thin gold foil used by Geiger and Marsden. Based on the results of their experiment, about how many of these α-particles are scattered through angles greater than \(1^\circ\)?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 700
Most α-particles go through the thin foil without any collision. Only a small part of the beam is turned through more than \( 1^\circ \). The experiment found this part to be about 0.14 % of the incident particles.
\( \begin{aligned} N &= \frac{0.14}{100}\times5.0\times10^{5} \\ &= 700 \end{aligned} \)
NCERT (2026-27):
Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom – “… Many of the α-particles pass through the foil. It means that they do not suffer any collisions. Only about 0.14% of the incident α-particles scatter by more than 1°; …”