Question:

The amount of energy released when one microgram of matter is annihilated is

Show Hint

Always convert mass to kg ($1 \text{ \mu g} = 10^{-9} \text{ kg}$) before using $E=mc^2$.
Updated On: Apr 10, 2026
  • 25 kWh
  • $9 \times 10^{10}$ kWh
  • $3 \times 10^{10}$ kWh
  • $0.5 \times 10^5$ kWh
Show Solution
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The Correct Option is A

Solution and Explanation

Step 1: Formula
Use Einstein's mass-energy equivalence: $E = mc^2$.
Step 2: Values

$m = 1 \text{ \mu g} = 10^{-9} \text{ kg}$.
$c = 3 \times 10^8 \text{ m/s}$.
$E = 10^{-9} \times (3 \times 10^8)^2 = 9 \times 10^7 \text{ J}$.
Step 3: Conversion

$1 \text{ kWh} = 3.6 \times 10^6 \text{ J}$.
$E = \frac{9 \times 10^7}{3.6 \times 10^6} = 25 \text{ kWh}$.
Final Answer: (a)
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