Uncertainty in the position of an electron moving with a velocity of 200 m/s, accurate up to 0.01%, will be: 

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DSSSB PGT Chemistry (Female) Official Paper (Held On: 06 Jul, 2018 Shift 1)
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  1. 2.9 × 10-3 m
  2. 2.9 × 10-2 m
  3. 2.9 × 10-5 m
  4. 2.9 × 10-1​ m

Answer (Detailed Solution Below)

Option 1 : 2.9 × 10-3 m
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Detailed Solution

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CONCEPT:

Heisenberg's Uncertainty Principle

  • Heisenberg's uncertainty principle states that it is impossible to simultaneously determine the exact position and exact momentum (or velocity) of a particle.
  • The uncertainty in position (Δx) and momentum (Δp) are related by:

    Δx × Δp ≥ h / 4π

    where h is Planck's constant (6.626 × 10-34 J·s).
  • Momentum (p) is given by:

    p = m × v

    where m is the mass and v is the velocity.
  • Uncertainty in momentum (Δp) can be calculated as:

    Δp = m × Δv

    where Δv is the uncertainty in velocity.

EXPLANATION:

  • Given:
    • Velocity of the electron (v) = 200 m/s
    • Accuracy of velocity = 0.01%
    • Mass of electron (m) = 9.1 × 10-31 kg
    • Planck's constant (h) = 6.626 × 10-34 J·s
  • Uncertainty in velocity (Δv):
    • Δv = (0.01 / 100) × 200
    • Δv = 0.02 m/s
  • Uncertainty in momentum (Δp):
    • Δp = m × Δv
    • Δp = (9.1 × 10-31) × (0.02)
    • Δp = 1.82 × 10-32 kg·m/s
  • Uncertainty in position (Δx):
    • Δx × Δp ≥ h / 4π
    • Δx ≥ h / (4π × Δp)
    • Δx ≥ (6.626 × 10-34) / (4 × 3.1416 × 1.82 × 10-32)
    • Δx ≥ 2.9 × 10-3 m

Therefore, the uncertainty in the position of the electron is approximately 2.9 × 10-3 m.

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