11 Wave Motion

Question 1

Determine direction of particle velocity

Answer 1

Check where the particle is at the next moment in time.

Special case: velocity is 0 at the amplitudes.

Question 2

Determine direction of particle acceleration

Answer 2

Particle acceleration is always opposite to displacement.

Special case: acceleration is 0 at equilibrium point

Question 3

Determine points of compression or rarefaction (for longitudinal waves)

Answer 3

On the displacement-distance graph, mark the displacement of particles.

Positive = right, Negative = left.

Question 4

Define Intensity of wave

Answer 4

The intensity of a wave is the rate of flow of energy per unit area perpendicular to the direction of the wave.

I = P/area

Question 5

Relationship between intensity of wave and amplitude

Answer 5

I ∝ A²

Question 6

Malus’s Law

(Intensity of beam passing through polariser)

Answer 6

I = I₀ cos²θ