Atomic physics

Traps in Atomic physics

• Chooses a true but irrelevant statement
  Re-read the question word (why, which, what causes). A true fact that answers a different question is still wrong.
• Picks a related law, device or effect with a different job
  Learn laws and devices as 'name → what it tells you' cards. Contrast neighbours: left-hand rule = motor force, right-hand rule = dynamo current, grip rule = field around a wire.
• Confuses alpha, beta and gamma changes
  α (⁴₂He): A−4, Z−2. β⁻ (⁰₋₁e): A unchanged, Z+1. γ: no change in A or Z.
• Reverses a relationship or direction
  Write the relationship with an arrow or proportionality sign first (E ∝ f; R ∝ L; cooling a metal → R falls). Then check the option follows the same direction.
• Takes part of the condition as the whole answer
  Check whether the option is enough on its own. Equilibrium needs zero resultant force AND zero total moment; a complete explanation names every factor in the stem.
• Puts a quantity or item in the wrong class
  Classify by the defining test: vector = has direction; charged radiation bends in a field; renewable = replaced naturally within a human lifetime.
• Mixes up a pair of similar physics terms
  Make a two-column table for each pair with one defining feature and an example. Underline the defining word in the stem before you look at the options.
• Uses everyday intuition instead of physics
  Name the law that applies (Newton's first law, Archimedes' principle, kinetic theory) and reason from it. If the option only 'feels' right, test it against the law.
• Uses the wrong arithmetic operation
  Write the formula symbolically and substitute only at the end. Check units: if the units of your answer are wrong, so is the operation.
• Electromagnetic spectrum order errors
  Increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-rays, gamma. All travel at 3 × 10⁸ m s⁻¹ in vacuum; shorter wavelength = higher frequency and energy.