IB Physics HL C.2 Wave model questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type

Multiple choice Written

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Question 1

Multiple choiceMedium1 mark

A source produces periodic waves in medium X with wavelength $\lambda$ period $T$ and speed $v$ The source is adjusted to produce waves with period $T/2$ in medium Y, where their speed is $3v$ What is the wavelength of the waves in medium Y?

Show answer and explanation

Answer: B. Since $v=f\lambda$ and $f=1/T$ wavelength is $\lambda=vT$ The wavelength in medium Y is $(3v)(T/2)=3vT/2=3\lambda/2$

A: applies the period change but leaves the wave speed unchanged.
C: applies the speed change but leaves the period unchanged.
D: uses $2T$ instead of $T/2$ then applies the speed factor of 3.

Remember: wavelength is the product of wave speed and period.

Question 2

Multiple choiceMedium1 mark

A travelling wave P has frequency $f$ and wavelength $\lambda$ A second travelling wave Q has the same speed as P and a frequency of $2f$ In Q, particles oscillate parallel to the direction of travel. Which description of Q is correct?

Show answer and explanation

Answer: C. Q is longitudinal because its particles oscillate parallel to the direction of travel. Since the two waves have the same speed, $v=f\lambda=(2f)\lambda_Q$ so $\lambda_Q=\frac{\lambda}{2}$

A: reverses the wave classification and treats wavelength as directly proportional to frequency.
B: finds the wavelength correctly but labels parallel oscillations as transverse.
D: identifies the wave correctly but uses a direct rather than inverse frequency–wavelength relationship.

Remember: at fixed wave speed, frequency and wavelength are inversely proportional.

Question 3

Paper 2Hard10 marks

A cord and a spring each carry a sinusoidal travelling disturbance along the equilibrium $x$ -axis. Figure 1 shows the displacement of particles from equilibrium at $t=0$ and $t=0.20\ \mathrm{s}$ plotted against each particle’s equilibrium coordinate $x$ In the upper panel, $y$ is the cord-particle displacement perpendicular to $x$ with positive $y$ upwards. In the lower panel, $u$ is the spring-particle displacement along $x$ with positive $u$ in the $+x$ direction. Each disturbance retains its profile as it travels.

(a)

Determine the direction of propagation and the speed of the disturbance on the cord.

[2]

(b)

State the wavelength of the disturbance on the cord.

[1]

(c)

At $x=0.20\ \mathrm{m}$ determine the instantaneous velocity of the cord particle at $t=0.20\ \mathrm{s}$ Give your answer with its direction.

[4]

(d)

The spring disturbance is now launched in the opposite direction, with its speed and wavelength unchanged. Describe how its profile at $t=0.20\ \mathrm{s}$ is displaced relative to its profile at $t=0$ State whether the disturbance is still longitudinal, and explain your answer.

[3]

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