Converting joules to SI prefix units

Steps:

• Write 0.0005 J as 5 × 10^{-4} J in scientific notation.
• Use prefix definitions: mJ = 10^{-3} J, μJ = 10^{-6} J, nJ = 10^{-9} J, pJ = 10^{-12} J.
• Convert 5 × 10^{-4} J to each unit by multiplying by 10^{exponent of prefix}.
• Results: 0.5 mJ, 500 μJ, 500,000 nJ, 500,000,000 pJ—none equal 5 of any option.

Why C is correct:

• None of the options are correct; 5 pJ = 5 × 10^{-12} J by definition of pico prefix (10^{-12}), which is 10^8 times smaller than 0.0005 J.

Why the others are wrong:

• A: 5 mJ = 5 × 10^{-3} J = 0.005 J, 10 times larger than 0.0005 J.
• B: 5 μJ = 5 × 10^{-6} J = 0.000005 J, 100 times smaller than 0.0005 J.
• D: 5 nJ = 5 × 10^{-9} J = 0.000000005 J, 10^5 times smaller than 0.0005 J.

Final answer: None of the above