IB Physics SL 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

Difficulty

Easy Medium Hard

Question 1

Multiple choiceMedium1 mark

The graph shows the displacement of particles of a cord at one instant. The wave travels in the $+x$ direction. Which row describes the particle motion and whether this wave can propagate through a vacuum?

	Particle motion relative to wave travel	Can propagate through a vacuum?
A.	Parallel	Yes
B.	Parallel	No
C.	Perpendicular	No
D.	Perpendicular	Yes

Show answer and explanation

Answer: C. The graph gives particle displacement along $y$ while the wave travels along $x$ therefore particle motion is perpendicular to the direction of travel. A wave that displaces particles of a cord is mechanical and requires a material medium, so it cannot propagate through a vacuum.

A: reads the horizontal position axis as the particle-motion direction and assumes the wave can travel without a medium.
B: reads the horizontal position axis as the particle-motion direction, giving parallel motion.
D: identifies the perpendicular motion correctly but mistakes a mechanical wave for one that can propagate through a vacuum.

Remember: mechanical waves require a medium; electromagnetic waves do not.

Question 2

Paper 2Medium8 marks

A laboratory compares a piezoelectric transducer producing sound in water with an antenna emitting electromagnetic radiation into a vacuum. Both waves have a frequency of $2.00\times10^6\ \mathrm{Hz}$

The speed of sound in water is $1.50\times10^3\ \mathrm{m\,s^{-1}}$ The speed of electromagnetic waves in a vacuum is $3.00\times10^8\ \mathrm{m\,s^{-1}}$

(a)

Calculate the wavelength of the sound wave in water.

[2]

(b)

Calculate the wavelength of the electromagnetic wave and, using the approximate wavelength orders of magnitude in the data booklet, identify its region of the electromagnetic spectrum.

[3]

(c)

Using your answers to (a) and (b), determine the ratio $\lambda_{\text{electromagnetic}}/\lambda_{\text{sound}}$

[1]

(d)

The two signals are directed across an evacuated region towards detectors. State which signal can cross the region and explain your answer with reference to the nature of each wave.

[2]

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