8.Some sunglasses are coated on one side with a thin film of MgF2 to reduce reflection from the glass surface. The index of refraction of MgF2 is 1.38; that of the glass is 1.50. What is the least coating thickness that eliminates (via interference) the reflections in the range of the visible spectrum (≒ 550nm)? Assume that the light is approximately perpendicular to the glass surface.
(A)40nm
(B)60nm
(C)80nm
(D)100nm
(E)120nm

4.A diffraction grating just resolves the wavelengths 400.0 nm and 400.1 nm in the first order. The number of slits in the grating is . (A)400 (B)1000 (C)2500 (D)3000 (E)4000

5.A clear sheet of polaroid is placed on top of a simmilar sheets so that their polarizing axes make an angle of 30° with each other. The ratio of the intensity of emerging light to incident unpolarized light its . (  cos30o,sin30o    ) (A)1/4 (B)1/3 (C)1/2 (D)3/4 (E)3/8

6.What is the intensity ratio of sound for the heavy truck at 1.5m(90dB) to normal conversation at 1m(60dB)? (A)1.5 (B)103 (C)0.67 (D)1030 (E)

7.What is the ratio of the shortest wavelength of the Balmer series to the shortest wavelength of the Lyman series in the spectrum of the Hydrogen atom? (A)2 (B)5 (C)3 (D)4 (E)9

9.The two headlights of a car are 1.4m apart. At what maximum distance will the eyes resolve them? Assume that the pupil diameter is 5.0mm, and use a wavelength of 550 nm for the light. (Consider only diffraction effects.) (A)3km (B)5km (C)10km (D)15km (E)20km Fig 1

10.A flute (which we treat as a pipe open at both ends) is 60cm long. How far from the mouthpiece should a hole be uncovered for the fundamental frequency to be 330Hz? (The speed of sound is 330m/s). (A)35cm (B)40cm (C)45cm (D)50cm (E)55cm

11.An ideal monatomic gas undergoes a quasistatic expansion to one-third of its initial pressure. Find the ratio of the final volume to the initial volume if the process is adiabatic. (0 = Cp / Cv 5/3 for ideal monatomic gas, log3 0.5) (A) (B)100.3 (C)100.5 (D)100.6 (E)100.7

12.A block with mass m 250g is fastened to a spring with spring constant k 85N/m. The system is excited to oscillate. Assume that there is a velocity-dependent damping force Fd -bv in the system with b 70g/s. How long does it take for the amplitude of the damped oscillation to drop to half its initial value? (ln2 0.693) (A)3s (B)4s (C)5s (D)6s (E)7s

13.A thin rod whose length L is 10cm and whose mass m is 100g, suspended at its midpoint from a long wire. Its period Ta of angular SHM (Simple Harmonic Motion) is measured to be 2.50 s. An irregularly shaped object is then hung from the same wire and its period Tb is found to be 5.0s. What is the rotational inertia of the irregular object about its suspension axis? (The rotational inertia for a rod is  mL2  ) (A) (B) (C) (D) (E)

14.In high-speed motion through air, the resisting force is approximately  F = cv2 . For a human body falling through air in a spread-eagle position, c is about 0.25kg/m. An 80kg sky diver jumps out of an airplane and reaches terminal speed before opening the parachute. What is the terminal speed? (A)49m/s (B)56m/s (C)72m/s (D)84m/s (E)98m/s