Waves, Electricity, Magnetism and Radioactivity
Waves
You must know transverse and longitudinal waves, amplitude, wavelength, frequency and wave speed. Use wave speed = frequency × wavelength. Learn reflection, refraction and the electromagnetic spectrum, including uses and dangers. A trap is mixing up frequency and wavelength; they are inversely related for a fixed speed.
Electricity
Understand series and parallel circuits, current, voltage and resistance. Use Ohm's law, V = IR, and power, P = VI. In series, current is the same everywhere; in parallel, voltage is the same across branches. A trap is adding resistances incorrectly in parallel.
Magnetism
Know magnetic poles, fields and electromagnets, and how a changing magnetic field induces a current. Motors and generators convert between electrical and kinetic energy.
Radioactivity
Learn alpha, beta and gamma radiation, their penetration and ionising power, and half-life. A trap is thinking half-life is the time for all activity to stop; it is the time for activity to halve.
Worked example
A sample has activity 80 counts per minute and a half-life of 5 days. After 15 days, three half-lives have passed: 80 → 40 → 20 → 10 counts per minute.
Practical Work, Data Handling and Investigation
Planning an investigation
You must identify variables: the independent variable you change, the dependent variable you measure, and control variables kept constant. Write a clear hypothesis and a method that another student could repeat. A trap is failing to control variables, which makes results invalid.
Measurement and apparatus
Choose suitable apparatus and read scales correctly, estimating to the smallest division. Know how to use a ruler, thermometer, balance, measuring cylinder, stopwatch and ammeter. Record readings in tables with units in the headings.
Data handling
Calculate means, identify anomalies and plot graphs with labelled axes and units. Draw a line of best fit. Describe trends using data, not vague words. A trap is describing a graph as "going up" without quoting values.
Accuracy, precision and errors
Random errors scatter readings; systematic errors shift them all in one direction. Repeat readings to improve reliability. Evaluate whether the evidence supports the conclusion, and suggest improvements.
Worked example
Three readings of a length are 4.2 cm, 4.3 cm and 4.8 cm. The 4.8 cm reading is an anomaly; the mean of the other two is 4.25 cm. State that repeats improve reliability and that the anomaly should be excluded with a reason.