Properties of Alpha and Beta Particles

Steps:

• Alpha particles are helium nuclei (mass 4, charge +2), beta particles are electrons (negligible mass, charge -1).
• Ionising effect depends on charge and mass: higher charge and mass cause more interactions with matter, leading to stronger ionisation.
• Penetrating power is inverse to ionising effect: particles that ionise more lose energy quickly and penetrate less.
• Thus, beta has weaker ionising effect (fewer interactions) and alpha has weaker penetrating power (stops sooner).

Why C is correct:

• Alpha's greater mass and charge (+2e) cause stronger ionisation per the interaction rate in matter, while beta's lower mass and charge (-e) result in weaker ionisation and higher penetration.

Why the others are wrong:

• A: Reverses both; alpha ionises more strongly than beta.
• B: Incomplete option, does not match properties.
• D: Correct on ionisation but wrong on penetration; alpha penetrates less than beta.

Final answer: C