पुढीलपैकी कोणती विधाने बरोबर आहेत ?
अ. गॅमा किरणोत्सार साध्या अल्युमिनिअम फॉईलने अडवता येतात.
ब. अल्फा किरणोत्सार कातडीने अडतो पण बीटा किरणोत्सार मात्र हाडांपर्यंत पोहोचू शकतो.
क. बीटा किरणोत्सार 20 इंच जाडीच्या काँक्रीटच्या भिंतीतून आरपार जाऊ शकतो.
ड. गॅमा किरणोत्सार शिशाची भिंत, स्टेनलेस स्टीलची भिंत किंवा काँक्रिटची भिंत अडवू शकते.

The correct answer is Option B (b and d).

Key Points:
• Penetrating Power of Nuclear Radiations (alpha, eta, gamma):
• Alpha (alpha) rays: Helium nuclei (⁴₂He²+) with the lowest penetration power; they are stopped by a sheet of paper or the human skin layer.
• Beta (eta) rays: High-speed electrons with moderate penetration; stopped by a few millimeters of aluminum sheet. They easily pass through skin and reach underlying body tissues and bones (Statement b is correct). They *cannot* penetrate a 20-inch concrete wall (Statement c is false).
• Gamma (gamma) rays: High-energy electromagnetic photons with enormous penetrating capability; simple aluminum foil cannot stop them (Statement a is false). They require dense shielding such as thick lead (Pb), heavy stainless steel, or thick concrete walls to attenuate them (Statement d is correct).
• Therefore, statements b and d are correct (Option 2).
• Key Takeaway: Alpha is stopped by skin, beta penetrates into tissues/bones, and gamma requires dense lead or concrete walls for shielding.