物理波的現象 DSE、CE 選擇題

1.

Circular wavefronts through two narrow gaps S1 and S2 in a barrier, with points P and Q marked

The figure above shows the wavefronts formed in a ripple tank. Solid lines represent crests. $S_1$ and $S_2$ are two narrow gaps allowing water waves to pass through and interfere. Which of the following statements is correct ?

2.

Two point sources $S_1$ and $S_2$ are producing circular water waves in a ripple tank. The figure shows the wave pattern at a certain instant. Solid lines represent crests and dotted lines represent troughs. Which of the following statements is/are correct ?

(1)The water particle at

A

is always at rest.

(2)The water particle at

B

is always at a crest.

(3)The interference at

C

is neither constructive nor destructive.

Circular wavefronts (solid for crests, dotted for troughs) from S1 and S2 with points A, B and C marked

3.

Water wave travelling towards a floating cork, with 0.4 m and 0.6 m distances marked

A cork is floating on a calm water surface as shown in the above figure. At time $t=0$ , a water wave is travelling towards the cork with a speed of $0.2\ \mathrm{m\,s^{-1}}$ . When will the cork rise to its highest position for the first time ?

4.

A musical note is produced by a guitar string. Which of the following properties about the sound wave produced and the wave in the string is/are the same ?

(1)wavelength

(2)frequency

(3)wave speed

5.

Circular wavefronts from two identical dot vibrators S1 and S2 with a point P marked

The figure above shows the circular wavefronts produced by two identical dot vibrators, $S_1$ and $S_2$ , in a ripple tank at time $t=0$ . Solid lines represent crests. A cork is placed at point $P$ on the water surface. Which of the following graphs best represents the variation of the displacement $s$ of the cork with time $t$ ? (Take upward as the positive direction.)

6.

Light from a source passing from air to water through a slit

Light travels from air to water through a slit as shown above. Which of the properties of the light in water remain(s) unchanged ?

(1)direction of travel

(2)speed

(3)frequency

7.

Wavefront PQ in medium A and P'Q' in medium B at a boundary

A series of plane waves travel from medium $A$ into medium $B$ . The figure above shows the positions, $PQ$ and $P^\prime Q^\prime$ , of a wavefront before and after entering the medium $B$ . What would happen to the speed and the wavelength of the wave when it travels from medium $A$ to medium $B$ ?

	Speed	Wavelength
	increases	increases
	increases	remains unchanged
	decreases	decreases
	decreases	remains unchanged

8.

Straight water waves travelling towards a barrier inclined at 30 degrees

Straight water waves travel towards a barrier as shown above. Which of the following diagrams best shows the reflected wave pattern ?

Four diagrams A to D of reflected wave patterns

9.

A cork floats in water and a dropper is used to produce circular waves as shown in the diagram. Which of the following describes the motion of the cork when the waves pass through it ?

A dropper releasing drops onto water with a floating cork

10.

An interference pattern is formed by two coherent point sources of water waves. Which of the following variations can change the positions of constructive interference ?

(1)changing the amplitude of the waves

(2)changing the wavelength of the waves

(3)changing the separation between the point sources