8. A spherical ball contains a charge +q uniformly distributed over its surface. When its diameter is D, the electric field at its surface has magnitude E. What will the electric field be if its diameter changes to 2D without changing the charge?
(A)E
(B)2E
(C)4E
(D) E/2
(E) E/4

4. Which statement of the energy carried by a photon is WRONG? (A) It is proportional to the photon frequency. (B) It is inversely proportional to the photon wavelength. (C) It is proportional to the photon mass. (D) All of the above are correct. (E) All of the above are wrong. 

5. A 1000 kg car traveling north at 15 m/s collides with a 2000 kg truck traveling east at 10 m/s. The two vehicles move away from the impact point as one. What is the velocity of the wreckage just after impact? (A)0m/s(B) 8.3 m/s(C)5.0 m/s (D) 6.6 m/s (E) 1.7 m/s

6. When a mass attached to a spring is stretched by an amount x away from its equilibrium position, it oscillates with frequency f. What is the oscillation frequency if the mass is instead released 2x from its equilibrium position? (A)f/2 (B)f (C)(D)2f (E)4f

7. Two wavesare sent to a long string to create a standing wave. Let x be positive (x ≥ 0). Where is the first node (the smallest value of x)? (A) 5 cm (B) 10 cm (C)50 cm (D) 100 cm (E) 200 cm

9. What is the total energy supplied while the current increases from zero to a final value I? Assume L is the inductance. (A)(B)LI2 (C) 2LI2 (D)(E)4LI2

10. An object is placed between two mirrors of distance apart. If object  is distance away from mirror 1 (see the right figure), what is the distance of the second closest image of object  that appears in mirror 1? (Hint: The closest one is .) (A)(B)28/3 (C)  (D)4 (E) 5

11. Which of the following statements on radioactive decays is true? (A) The rate of decary is proportional to the number of undeeayed substance. (B) The rate of decay  is proportional to the half-life of the undecayed substance. (C) The decay constant is proportional to the half-life of the undecayed substance. (D) The half-life of a substance decreases with time. (E) None of the above. 

12. A force produces potential U(x) = ax4. where a = 1.43 J/m4 . What is the force and direction when the particle is at x = -0.78 m? (A)ON (B)-0.67 N (C) 0.67N (D) -2.7 N (E) 2.7 N

13. In vacuum, an electromagnetic wave traveling along the x axis has an electric field and a magnetic field whose magnitudes depend on x and t asE(x,t)=E0sin(kx一ωt),B(x,t)=B0sin(kx-ωt+Φ), where E0 and B0 are the amplitudes of . Which fact below is correct? (A) (B)The directions of  and   are arbitrary once they are perpendicular to x. (C)Φ=π/2 (D) ωk =c (E)This is a linearly polarized wave.

14. Which statement regarding total internal retlection is not true? (A) It cannot occur when the incident light is in the medium of lower index of refraction. (B) Total internal reflection oceurs for rays with their incident angles greater a critical angle. (C) It explains the phenomenon that the water-to-air interface looks like a mirror when an observer is in water. (D) It is used in transmission through optical fibers. (E) The effect is used to realize polarizers.