物理 1999 年 DSE、CE 選擇題（第 2 頁）

11.

Beaker of liquid with immersion heater connected to a power supply, standing on an electronic balance

The above apparatus is used to find the specific latent heat of vaporization of a liquid. Which of the following can improve the accuracy of the experiment ?

12.

A cylinder contains a fixed mass of gas at a pressure of $10^5$ N m $^{-2}$ and a temperature of $27^\circ$ C. The cylinder is compressed to half of its original volume and the pressure increases to $3\times10^5$ N m $^{-2}$ . Find the final temperature of the gas.

13.

Figure (a): mechanical model of a gas with disc, ball bearings and motor-driven vibrating platform; Figure (b): P-V graph with initial state X and points A, B, C and D around it

Figure (a) shows a mechanical model of a gas and Figure (b) shows the $P$ - $V$ relation of a fixed mass of ideal gas at a certain temperature. If the operating voltage of the motor in the model is increased, which of the following denotes a corresponding transition in the $P$ - $V$ graph (point $X$ represents the initial state of the gas) ?

14.

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.

15.

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

16.

Straight water waves in a ripple tank on the left, a question mark in the middle region, and curved waves on the right

A series of straight water waves travels towards the right in a ripple tank as shown above. In order to obtain the waves in the right hand side, what kinds of phenomenon have the straight waves undergone ?

17.

A plane water wave travels from a deep region to a shallow region of water. If the wavelength, frequency and speed of the wave in the deep region are $\lambda_1$ , $f_1$ and $v_1$ respectively, while the corresponding values in the shallow region are $\lambda_2$ , $f_2$ and $v_2$ respectively. Which of the following relations is/are correct ?

(1)

\lambda_1>\lambda_2

(2)

v_1>v_2

(3)

f_1>f_2

18.

Which of the following equipment emit(s) waves which are electromagnetic in nature ?

(1)a television remote control

(2)a microwave oven

(3)an ultrasonic scanner for examining foetuses (babies not yet born)

19.

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.

20.

An insulated metal sphere carries positive charges. Which of the following will discharge the sphere ?

(1)bringing an alpha source near the sphere

(2)touching the sphere momentarily with a finger

(3)bringing a negatively charged metal rod near the sphere (but without touching it)