## Technical terms

Teaching Guidance for 14-16

#### Defining new terms: superposition and interference

From a teaching and learning point of view it is well worth the time and effort to introduce new terms carefully.

When two sets of waves interact and combine, the phenomenon is termed superposition

and the waves are said to interfere

.

If the two sets of waves are directly in phase (or in step) at a certain point, the wave amplitudes add together and full constructive interference

occurs.

If the two sets of waves are directly out of phase (or out of step) at a certain point, the wave amplitudes cancel each other out and full destructive interference

occurs.

**Teacher Tip: **If two contributions superpose then there is interference.

**Teacher Tip: **Contributions out of step are out of phase: Superposition → destructive interference.

**Teacher Tip: **Contributions in step are in phase: Superposition → constructive interference.