NEETPhysicsAtomic Physics
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In the Geiger-Marsden experiment, for a given impact parameter and incident kinetic energy, a target nucleus with a larger atomic number ( Z ) will scatter an -particle by a larger angle. Reason (R): The Coulomb repulsive force between the -particle and the target nucleus is inversely proportional
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
C. (A) is true but (R) is false
Step-by-step solution
The impact parameter b is given by the relation b = Z e^2 ( /2) 4 ₀ K . For a fixed impact parameter b and incident kinetic energy K , the product Z ( /2) is constant. If the atomic number Z increases, ( /2) must decrease. Since ( /2) is a decreasing function for angles between 0^ and 90^ , the scattering angle must increase. Thus, the Assertion (A) is true. The Coulomb repulsive force between an -particle (charge 2e ) and a nucleus (charge Ze ) is F = 1 4 ₀ (2e)(Ze) r^2 . This force is directly proportional to the