物理聲音 DSE、CE 選擇題（第 3 頁）

21.

The figure shows the image of a foetus (a baby not yet born) taken by a scanner. Which of the following waves should be used in the scanning process ?

22.

CRO displays of Note X (complex waveform) and Note Y (sinusoidal waveform)

The above figures show the CRO displays of two musical notes $X$ and $Y$ . The settings of the CRO for the two notes are identical. Which of the following statements are correct ?

(1)Notes

X

and

Y

are of different qualities.

(2)Note

X

is of a higher pitch than note

Y

.

(3)Note

X

is louder than note

Y

.

23.

Which of the following is **not** a transverse wave ?

24.

A sonar on a ship is used to find the depth of the sea. An ultrasonic wave pulse is sent downwards from the ship towards the sea bed. The pulse travels with a speed of $1500\ \mathrm{m\,s^{-1}}$ in sea water. If the reflected pulse is received after $0.16$ s, find depth of the sea.

25.

Which of the following statements about light and sound is/are correct ?

(1)Both light and sound are transverse waves.

(2)Both light and sound travel faster in air than in water.

(3)Both light and sound can undergo refraction when travelling from one medium to another.

26.

Which of the following statements about ultrasonic waves is correct ?

27.

Which of the following statements concerning microwaves and ultrasonic waves is/are correct ?

(1)Microwaves are electromagnetic waves while ultrasonic waves are not.

(2)Microwaves and ultrasonic waves travel with the same speed in air.

(3)Microwaves can be diffracted while ultrasonic waves cannot.

28.

When a sound wave travels from air into water, its wavelength is increased by five times. If the speed of sound in air is $330\ \mathrm{m\,s^{-1}}$ , find the speed of the sound wave in water.

29.

Which of the following is NOT an application of ultrasonics ?

30.

The frequencies of two musical notes $X$ and $Y$ are $256$ Hz and $512$ Hz respectively. If $X$ and $Y$ both have the same amplitude, which of the following statements is/are true ?

(1)

Y

has a higher pitch than

X

.

(2)The loudness of

X

is larger than that of

Y

.

(3)The wavelength of

Y

is longer than that of

X

.