物理波的現象 DSE、CE 選擇題（第 5 頁）

41.

Stationary wave on a string at the instant of maximum displacement (one half cycle shown)

A stationary wave is formed in a string. The above diagram shows the string at the instant of maximum displacement. What will be the shape of the wave pattern one quarter of a period later ?

42.

In a ripple tank, when water waves pass through a narrow gap in a barrier, what happens to its frequency and wavelength ?

	Frequency	Wavelength
	increases	decreases
	decreases	increases
	decreases	remains unchanged
	remains unchanged	remains unchanged

43.

The figure shows a stationary water wave at its maximum vibration. What is the direction of the motion of a particle $P$ at this instant ?

One cycle of a stationary wave with point P on the right-hand crest side

44.

Straight waves in a ripple tank are observed using a hand stroboscope with a single slit. The maximum frequency of rotation of the stroboscope where a stationary pattern can be observed is $2$ revolutions per second. The distance between the first crest and the eleventh crest is found to be $0.2$ m. What is the speed of the wave ?

45.

A stationary wave is produced in a string by a vertical vibrator as shown in the diagram. If $P$ is the crest of an antinode, what is the direction of motion of the point $A$ at that instant ?

Stationary wave on a string between a vibrator and a wall, P at a crest and A just to the right of P

46.

In a ripple tank experiment, a series of plane water waves are sent through a narrow slit. Which of the following will have changed when the water waves emerge from the slits ?

(1)wave speed

(2)wave pattern

(3)frequency

47.

A stationary wave is set up along a string by a vibrator as shown in the diagram. If the frequency of the vibrator is $5$ Hz, what is the velocity of the wave set up in the string ?

Stationary wave on a string with four loops spanning 20 cm

48.

A train of water waves is travelling from a deep water region to a shallow water region. Which of the following properties of the water waves will be changed ?

(1)wavelength

(2)frequency

(3)velocity

49.

A stationary wave is obtained by attaching one end of a string to a $50$ Hz vibrator as shown in the diagram. The velocity of the waves propagated in the string is

Stationary wave on a string between a vibrator and a fixed end, two loops spanning 0.1 m