物理 1992 年 DSE、CE 選擇題（第 2 頁）

11.

The refractive indices of water and glass are $1.33$ and $1.5$ respectively. In which of the following cases will total internal reflection occur ?

Three cases of an incident ray at 50 degrees: (1) air to glass, (2) water to air, (3) water to glass

12.

An immersion heater is used to heat a cup of water. It takes $10$ minutes to bring the water from $20^\circ\mathrm{C}$ to its boiling point $100^\circ\mathrm{C}$ . Find the time taken for the heater to vaporize the boiling water completely. (Given : specific heat capacity of water $= 4200\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$ specific latent heat of vaporization of water $= 2.268\times10^6\ \mathrm{J\,kg^{-1}}$ .)

13.

If the volume of a fixed mass of gas is reduced at constant temperature, the pressure of the gas increases. Which of the following correctly account(s) for the increase in pressure ?

(1)The gas molecules hit the container wall more frequently.

(2)The average spacing between the gas molecules increases.

(3)The average speed of the gas molecules increases.

14.

Capillary tube with mercury thread trapping a gas column, with thermometer, in a beaker of water heated from below

The apparatus shown in the figure is used to study the relation between the volume and temperature of a fixed mass of gas at constant pressure. Which of the following statements is/are correct ?

(1)Immersing the whole gas column in water.

(2)Sealing the capillary tube at both ends.

(3)Preventing the thermometer from touching the bottom of the beaker.

15.

Thermometer and electric heater immersed in water in a beaker

In the diagram shown, the water is initially at room temperature. The electric heater is switched on for $300$ s and then switched off. Which of the following graphs correctly describes the variation of the reading of the thermometer ?

16.

Gas column in a cylinder compressed by a piston

A column of gas is compressed slowly as shown in the figure above. Which of the following graphs correctly shows the relation between the gas pressure $P$ and the length of the gas column $h$ ?

Four graphs: A P against h straight line; B P against h line with negative intercept; C P against 1/h curve; D P against 1/h straight line through the origin

17.

Water wave travelling to the right with P at a crest, Q on the equilibrium line and R at a trough

A water wave travels towards the right. The above diagram shows the waveform at a certain instant. Which of the following statements is/are true ?

(1)Particle

P

is moving downwards.

(2)Particle

Q

is moving upwards.

(3)Particle

R

is momentarily at rest.

18.

Which of the following is/are longitudinal waves ?

(1)Ultrasonic transmitted through air.

(2)Infrared transmitted through water.

(3)Gamma rays transmitted through outer space.

19.

In a ripple tank experiment, the pattern of plane water waves is frozen by using a stroboscopic lamp flashing at a frequency of $50$ Hz as shown in the above diagram. If the frequency of the vibrator is $50$ Hz, find the wavelength and speed of the waves.

Frozen pattern of plane water waves with four wavelengths spanning 20 cm

	Wavelength	Speed
	$4$ cm	$2\ \mathrm{m\,s^{-1}}$
	$4$ cm	$12.5\ \mathrm{m\,s^{-1}}$
	$5$ cm	$2.5\ \mathrm{m\,s^{-1}}$
	$5$ cm	$10\ \mathrm{m\,s^{-1}}$

20.

Source S, double slits P and Q, and a point M with PM = 53 cm and QM = 50 cm

In a double-slit experiment, a source $S$ sends waves towards two slits $P$ and $Q$ , which are equidistant from $S$ . The distances of a point $M$ from $P$ and $Q$ are $53$ cm and $50$ cm respectively. If constructive interference occurs at $M$ , the possible wavelength of the waves is