IB Physics SL C.3 Wave phenomena 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

Difficulty

Easy Medium Hard

Question 1

Multiple choiceMedium1 mark

A plane wave crosses a straight boundary from medium 1 into medium 2. What is the ratio $\lambda_2/\lambda_1$

Show answer and explanation

Answer: D. Each ray is perpendicular to its wavefronts, so the angles to the normal are $\alpha$ and $\beta$ Frequency is unchanged at the boundary, so $\lambda_2/\lambda_1=v_2/v_1$ From Snell’s law, $n_1\sin\alpha=n_2\sin\beta$ and $n=c/v$ giving $v_2/v_1=n_1/n_2=\sin\beta/\sin\alpha$
A: reverses the incident-to-transmitted ratio.
B: uses the angle ratio instead of the sine ratio.
C: treats the marked angles as angles between rays and the boundary, rather than between wavefronts and the boundary.
Remember: the angle between a wavefront and the boundary equals the angle between its ray and the normal.

Question 2

Paper 2Medium9 marks

Two transverse pulses travel in opposite directions along the same string. At one instant, they overlap. The individual displacements of the pulses at three positions on the string are shown below. Displacements are measured from the equilibrium position; upward displacements are positive.

Position, x / cm	Pulse A displacement / cm	Pulse B displacement / cm
1.0	+2.0	+1.0
2.0	+4.0	−4.0
3.0	+2.0	−1.0

(a)

State the displacement of pulse A at x = 2.0 cm.

[1]

(b)

Determine the displacement of the string at each of the three positions.

[3]

(c)

Identify whether the interference at x = 3.0 cm is constructive or destructive. Explain your answer using the data.

[2]

(d)

At x = 2.0 cm, the resultant displacement is zero. Explain why this does not mean that the pulses have been destroyed, and describe their motion and shape once they have passed through one another completely.

[3]

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