物理波的傳播 DSE、CE 選擇題（第 2 頁）

11.

Questions 34 and 35 : The displacement-distance graphs of the particles along a travelling wave at time $t=0$ and $t=0.2$ s are shown below.

Two displacement-distance graphs on grids (2 cm squares), at t = 0 and t = 0.2 s

What is the speed of the wave ?

12.

The solid curve in the diagram shows a transverse wave at a certain instant. After $0.05$ s, the wave has travelled a distance of $2$ cm and is indicated by the dashed curve. Find the wavelength and frequency of the wave.

Solid and dashed transverse waves on a grid of vertical lines, shifted by 2 cm

	Wavelength / cm	Frequency / Hz
	8	2.5
	8	5
	16	2.5
	16	5

13.

Questions 25 and 26 : A transverse wave travels along a string with a speed of $1.2\ \mathrm{m\,s^{-1}}$ . The diagram below shows the shape of the string at a certain instant.

Displacement (cm) against distance (cm) graph of a wave moving to the right, amplitude 3 cm, wavelength 20 cm

Which of the following statements about the transverse wave are correct ?

(1)Its wavelength is

20

cm.

(2)Its frequency is

6

Hz.

(3)Its amplitude is

6

cm.

14.

Questions 25 and 26 : A transverse wave travels along a string with a speed of $1.2\ \mathrm{m\,s^{-1}}$ . The diagram below shows the shape of the string at a certain instant.

Which of the following diagrams shows the shape of the string at a quarter of a period later ?

Four displacement-distance graphs A to D

15.

A wave source generates waves of frequency $50$ Hz. How long does it take for the waves to travel $100$ m ?

16.

Water wave moving to the left with corks P, Q, R and S on the surface

Four corks are moving up and down on the surface of a pond as a water wave passes through them. At time $t=0$ , the positions of the corks are shown above. The figure below shows the displacement-time graph of one of the four corks. (Note : Displacement is positive when the cork is above the still water surface.)

Displacement against time graph starting at zero and rising first

Which cork has the motion represented by the graph ?

17.

Which of the following statements correctly describe(s) the meaning of the frequency of a wave ?

(1)the time taken for the wave to make one complete vibration

(2)the distance travelled by the wave in one second

(3)the number of waves produced in one second

18.

A cork in the water vibrates up and down $4$ times in $2$ s when a wave passes through it. The distance between two successive crests of the wave is $10$ cm. Find the speed of the water wave.

19.

The diagram shows a transverse wave travelling along a string. At the instant shown, particle $P$ is moving upwards. Which of the following statements is incorrect ?

Transverse wave with particles P, R and Q marked

20.

Figure (a): shape of string with wavelength x. Figure (b): displacement-time graph of a particle with period y

A vibrator generates a wave on a string. Figure (a) shows the shape of the string at a certain instant. Figure (b) shows the variation of the displacement of a certain particle on the string with time. Which of the following expressions represents the speed of the travelling wave ?