大学物理双语2012-2013-1月A

Constants

Plank’s constantsJh•341063.6, sJ•341005.1

Boltzmann’s constant KJk/1038.123

Gas constant KmolJR•/315.8

Electron rest mass kgme311011.9

Speed of light in vacuum smc/1000.38

一、Choice (4pts*5)

1. Free expansion. A adiabatic

container has two parts connected by

a valve (阀门). The volume of the

two parts is the same ( Fig.1 ). The

left part is filled with ideal gas

(diatomic molecule 双原子分子)

with temperature T. When the valve is opened, the gas will expand freely to fill both

parts. After the system reach thermal equilibrium, the temperature of the gas is ()

(a) T (b) 2/T (c) 3/22/T (d) T2

2 A red star and a blue star, which has higher surface temperature?

(a) The red star (b) The blue star

(c) They have the same surface temperature (d) Unable to determine

3. A particle’s location is measured and specified as being exactly at x = 0, with zero

uncertainty in the x direction. How does that location affect the uncertainty of its

momentun component in the y direction?

(a) It does not affect it. (b) It makes it infinite. (c) It makes it zero.

4. Unpolarized light passes through two polarizers whose optical axes are in the same

direction. The intensity of the emerging light is I0. If a third polarizer is placed

between the polarizers so that its axis is at an angle  with the other two, the intensity

of the emerging light is

(a) zero (b) I0 (c) I0 cos2 (d) I0 cos4

5. The following functions may represent the wave motion f(x,t) in a one-dimensional elastic

medium in terms of position x, time t, and positive constants A, a, and b. Which function

represents a traveling wave moving in the negative x-direction?

(a) btaxAtxfsin, (b) btaxAtxfsin,

(c) btaxAtxfcoscos, (d) btaxAtxfsinsin,

Fig.1

二、Blanks (20pts)

6. (8 pts) A 500 g mass is undergoing simple harmonic oscillation that is described by

the following equation for its position x(t) from equilibrium:

rad0.6rad/s0.6cos)m50.0()(ttx

The amplitude A of the oscillation is m. The frequency of the oscillation is Hz.

The period T of the oscillation is s. The phase of oscillator at t = 0 s is rad.

The maximum speed of the oscillator is m/s .

7. (3pts) When Newton ring apparatus is immersed in a liquid, the diameter of the

eighth dark ring decreases form 2.92cm to 2.60cm, the refractive index of the liquid

is .

8. (3pts) In single slit diffraction experiment, 680nm light falls on a slit 0.0345mm

wide. The angular width of the center diffraction peak is .

9. (3pts) The angular separation of the two components of a double star is 8×10-3 rad

and the light from the double stat har a wavelength of 550 nm. According to the

Rayleigh criterion, the smallest diameter of a telescope mirror that will resolve the

double star is ______ m.

10. (3pts) The De Broglie wavelength of a electron moving at 5.9×106m/s is .

三、Questions (10pts)

11. (5pts) The oceans contains a tremendous amount of thermal energy. Why, in

general, it is not possible to put it into useful work.

12. (5pts) what are the two postulates of Einstein’s Special Theory of Relativity?

四、Problems (50pts)

13. (10pts) For 1 mole O2 at room temperature (20℃),

(1) what is the average transitional kinetic energy of the molecules?

(2) what is the rms speed of the molecules?

(3) what is the internal energy of the gas?

14. (10pts) The PV diagram of the cycle in Carnot’s engine is shown in Fig 2. The

Carnot cycle has 4 processes:

12: Isothermal expansion with addition of heat |QH|;

23: Adiabatic expansion;

34: Isothermal compression with heat |QL| flowing out;

41: Adiabatic compression.

(1) Calculate |QH| and |QL|. (Suppose the gas is n mole)

(2) Show that the efficiency of Carnot engine is

HLTT1

Fig.2

15 (17pts) In the double - slit interference experiment (Fig. 3a), 550 nm light falls on

the double-slit with two very narrow slit 0.10 mm apart. A viewing screen is 1.0 m far

from the double-slit.

(1) What is the separation between the 2nd-order bright fringe and the 3rd-order

bright fringe?

(2) A thin flake of mica (云母, n=1.58) is used to cover one slit of a double – slit (Fig.

3b). The central point on the viewing screen is now occupied by what had been the

seventh bright slid fringe (m=7) before the mica was used. What is the thickness L of

the mica?

(3) Is the separation between adjacent bright fringes changed?

16 (13 pts) A 1 kg mass oscillates on the end of a spring whose spring constant is k=2500N/m. If

this system is in a spaceship moving pass the Earth with a speed of 0.8c, what’s the period of the