order of Magnitude — NEET Physics MCQs with Solutions
Free NEET Physics order of Magnitude MCQs with step-by-step solutions (22 questions). Part of Units and Dimensions. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — order of Magnitude · easy · theory
The order of magnitude of a number is
A. The first digit
B. The power of 10 nearest to it when written as $a×10^b$ with $1 \le a < 10$ ✓ Correct
C. The last digit
D. The number of digits
Solution: It is the exponent $b$ (rounded appropriately) in standard/scientific form.
Q2 — order of Magnitude · easy · numerical
The order of magnitude of 8000 is
A. $10^2$
B. $10^3$
C. $10^4$ ✓ Correct
D. $10^5$
Solution: 8000 = 8×10³; since 8 ≥ 5, we round up to 10×10³ = 10⁴.
Q3 — order of Magnitude · easy · numerical
The order of magnitude of 2500 is
A. $10^4$
B. $10^2$
C. $10^5$
D. $10^3$ ✓ Correct
Solution: 2500 = 2.5×10³; since 2.5 < 5, the order of magnitude is 10³.
Q4 — order of Magnitude · easy · numerical
The order of magnitude of 0.0007 is
A. $10^{-7}$
B. $10^{-3}$ ✓ Correct
C. $10^{-2}$
D. $10^{-4}$
Solution: 0.0007 = 7×10⁻⁴; since 7 ≥ 5, round up to 10⁻³.
Q5 — order of Magnitude · easy · numerical
The order of magnitude of the speed of light (3×10⁸ m/s) is
A. $10^9$
B. $10^7$
C. $10^{10}$
D. $10^8$ ✓ Correct
Solution: 3×10⁸ has 3 < 5, so the order of magnitude is 10⁸.
Q6 — order of Magnitude · easy · theory
To express a number in standard (scientific) form $a×10^b$, the value of $a$ satisfies
A. $a > 10$
B. $0 \le a < 1$
C. $a$ can be anything
D. $1 \le a < 10$ ✓ Correct
Solution: The mantissa $a$ is chosen between 1 (inclusive) and 10 (exclusive).
Q7 — order of Magnitude · easy · numerical
The order of magnitude of the charge of an electron (1.6×10⁻¹⁹ C) is
A. $10^{-16}$
B. $10^{-20}$
C. $10^{-18}$
D. $10^{-19}$ ✓ Correct
Solution: 1.6 < 5, so the order of magnitude is 10⁻¹⁹.
Q8 — order of Magnitude · medium · numerical
The order of magnitude of 6.6×10⁻³⁴ (Planck constant) is
A. $10^{-35}$
B. $10^{-33}$ ✓ Correct
C. $10^{-34}$
D. $10^{-32}$
Solution: 6.6 ≥ 5, so it rounds up to 10⁻³³.
Q9 — order of Magnitude · easy · numerical
0.00045 in scientific notation is
A. $0.45×10^{-3}$
B. $45×10^{-5}$
C. $4.5×10^{-3}$
D. $4.5×10^{-4}$ ✓ Correct
Solution: Move the decimal 4 places right: 4.5×10⁻⁴.
Q10 — order of Magnitude · easy · numerical
73000 in scientific notation is
A. $7.3×10^3$
B. $0.73×10^5$
C. $73×10^3$
D. $7.3×10^4$ ✓ Correct
Solution: Standard form has one non-zero digit before the decimal: 7.3×10⁴.
Q11 — order of Magnitude · easy · numerical
The order of magnitude of the radius of a hydrogen atom (≈ 5×10⁻¹¹ m) is
A. $10^{-9}$
B. $10^{-11}$
C. $10^{-10}$ ✓ Correct
D. $10^{-12}$
Solution: 5×10⁻¹¹: since 5 ≥ 5, round up → 10⁻¹⁰.
Q12 — order of Magnitude · easy · numerical
The number 3.2×10⁵ multiplied by 2×10³ gives
A. $6.4×10^2$
B. $6.4×10^{15}$
C. $6.4×10^8$ ✓ Correct
D. $5.2×10^8$
Solution: Multiply mantissas (3.2×2 = 6.4) and add exponents (5+3 = 8): 6.4×10⁸.
Q13 — order of Magnitude · easy · numerical
$\frac{8×10^6}{4×10^2}$ equals
A. $2×10^3$
B. $2×10^4$ ✓ Correct
C. $2×10^8$
D. $4×10^4$
Solution: Divide mantissas (8/4 = 2), subtract exponents (6−2 = 4): 2×10⁴.
Q14 — order of Magnitude · easy · theory
Order-of-magnitude estimation is used mainly to
A. Count significant figures
B. Measure error
C. Get an exact value
D. Get a rough, quick idea of the size of a quantity ✓ Correct
Solution: It gives an approximate scale, useful for sanity checks and estimates.
Q15 — order of Magnitude · easy · numerical
The order of magnitude of the mass of an electron (9.1×10⁻³¹ kg) is
A. $10^{-30}$ ✓ Correct
B. $10^{-31}$
C. $10^{-29}$
D. $10^{-32}$
Solution: 9.1 ≥ 5, so round up: 10⁻³⁰.
Q16 — order of Magnitude · easy · theory
0.0000000001 m equals
A. $10^{-9}$ m
B. $10^{-8}$ m
C. $10^{-10}$ m (1 Å) ✓ Correct
D. $10^{-12}$ m
Solution: There are 10 zeros, giving 10⁻¹⁰ m, which is 1 angstrom.
Q17 — order of Magnitude · easy · numerical
The order of magnitude of the diameter of the Sun (≈ 1.4×10⁹ m) is
A. $10^{10}$
B. $10^9$ ✓ Correct
C. $10^8$
D. $10^{11}$
Solution: 1.4 < 5, so the order of magnitude is 10⁹.
Q18 — order of Magnitude · easy · numerical
Written in scientific notation, 0.06 is
A. $6×10^{-3}$
B. $6×10^{-1}$
C. $6×10^{-2}$ ✓ Correct
D. $0.6×10^{-1}$
Solution: Move the decimal 2 places right: 6×10⁻².
Q19 — order of Magnitude · easy · numerical
Estimating the number of seconds in a day (86400 s), the order of magnitude is
A. $10^3$
B. $10^5$ ✓ Correct
C. $10^6$
D. $10^4$
Solution: 86400 = 8.64×10⁴; since 8.64 ≥ 5, round up → 10⁵.
Q20 — order of Magnitude · easy · numerical
The order of magnitude of the Avogadro number (6×10²³) is
A. $10^{25}$
B. $10^{22}$
C. $10^{24}$ ✓ Correct
D. $10^{23}$
Solution: 6 ≥ 5, so round up: 10²⁴.
Q21 — order of Magnitude · easy · numerical
$2×10^{-3}$ expressed as a decimal is
A. 0.002 ✓ Correct
B. 0.2
C. 0.02
D. 0.0002
Solution: 10⁻³ = 0.001, so 2×10⁻³ = 0.002.
Q22 — order of Magnitude · easy · theory
A quantity is 3×10⁴ and another is 2×10⁶. The second is larger than the first by a factor of
A. About 2
B. About 1000
C. About 67 (order 10²) ✓ Correct
D. About 10
Solution: $\frac{2×10^6}{3×10^4} ≈ 66.7$, i.e. roughly two orders of magnitude larger.