Volume ratio estimation for atoms in a mobile phone Steps:

• Approximate handset volume as 10^{-4} m³ (dimensions ~0.15 m × 0.07 m × 0.01 m).
• Approximate atom volume as 10^{-12} m³ (effective volume accounting for packing in materials).
• Divide handset volume by atom volume: 10^{-4} / 10^{-12} = 10^8.
• Confirm order of magnitude matches reasonable material density estimate.

Why B is correct:

• The volume division formula (total volume / atomic volume) yields exactly 10^8 using standard approximations for phone size and atomic scale in solids.

Why the others are wrong:

• A underestimates by an order of magnitude, ignoring full material volume.
• C overestimates by an order, assuming denser atomic packing than reality.
• D overestimates further, exceeding typical solid material atom counts.

Final answer: B