17. Electromagnetic standing waves are set up in a conducting cavity resonator in the form of a hollow metal box. The waves bounce back and forth between two parallel surfaces separated by 0.8 cm. What is the minimum resonant frequency for such a resonator?
(A) 3.30 GHz
(B) 4.42 GHz
(C) 12.4 GHz
(D) 15.5 GHz
(E) 18.8 GHz

13. A proton is projected toward a fixed nucleus of charge +Ze with velocity V0 . Initially the two particles are very far apart.When the proton is at a distance R from the nucleus, its velocity has decreased to1/2 V0 .How far from the nucleus will the proton be when its velocity has dropped to1/4 V0? (A) 1/16 R (B) 1/4 R (C) 1/2 R (D) 4/5 R (E) 6/7 R

14. An important observation that led Bohr to formulate his model of the hydrogen atom was the fact that . (A) the emission of light by an atom did not appear to conserve energy. (B) electrons were found to have a wave nature. (C) the peak of the blackbody radiation moved to shorter wavelengths as the temperature was increased. (D) neutrons formed a diffraction pattern when scattered from a nickel crystal. (E) a low density gas emitted a series of sharp spectral lines.

15. If the peak electric field in an electromagnetic wave is 1200 V/m , what is the peak magnetic field for the same wave? (A)2.2×10−6T  (B)3.4×10−6T (C)4.0 ×10−6T(D)8.7×10−6T (E)9.6×10−6T

16. The square plates of a 9000 pF capacitor measure 90 mm by 90 mm and are separated by a dielectric which is 0.29 mm thick. The voltage rating of the capacitor is 300 V. The dielectric strength of the dielectric, in kV/m , is closest to . (A) 930 (B) 1000 (C) 1100 (D) 1200 (E) 1300

18. The potential energy function of a particle moving in one dimension is U=kx2e−x2/a2where  a = 7.50nm . At what value of x is a point of stable equilibrium located? (A) 6.81 nm (B) 7.50 nm (C) 7.80 nm (D) 11.03 nm (E) 12.62 nm

19. A proton with speed  v = 3.00×105m/s orbits just outside a charged sphere. The radius of the orbit is 1.0 cm. What is the charge on the sphere? (The mass of a proton is 1.67×10−27kg.) (A)1.04×10−9C  (B)3.47×10−8C (C)6.23×10−8C (D)6.50×10−8C (E)8.28×10−7C

20. A 1.0µF capacitor with an initial stored energy of 0.50 J is discharged through a 1.0 MΩ resistor. What is the current through the resistor when the discharge starts? (A)1.0×10−3A  (B)2.0×10−3A  (C)1.0×10−2A  (D)2.0×10−2A  (E)5.0×10−2A 

21. A hollow sphere of inner radius 8.0 cm and outer radius 9.0 cm floats half-submerged in a liquid of density 800kg/m3 . What is the density of the material of which the sphere is made? (A)1.1×103kg/m3  (B)1.3×103kg/m3(C)1.8×103kg/m3 (D)2.4×103kg/m3 (E)4.8×103kg/m3

22. Three sinusoidal waves of the same frequency travel along a string in positive direction of an x axis. Their amplitudes are y1 ,y1/ 2and y1/3 , and their phase constants are 0, π/2, and π, respectively. What is the phase constant of resultant wave? (A) 30° (B) 37° (C) 45° (D) 53° (E) 60°

23. A girl is sitting near the open window of a train that is moving at a velocity 10.00m/s to the east. The girl’s uncle stands near the tracks and watches the train move away. The locomotive whistle emits sound at the frequency of 500.0 Hz. The air is still. What frequency does the uncle hear? (The speed of sound is 343m/s.) (A) 471.7 Hz (B) 485.8 Hz (C) 500.0 Hz (D) 515.0 Hz (E) 530.0 Hz