PHYSICS 202 EXAM 3 March 31, 2005

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1 PHYSICS 202 EXAM 3 March 31, 2005 NAME: SECTION: Note: 517 Recitation Mon 4: Recitation Wed 10: Recitation Wed 8: Recitation Mon 1:50 There are a total of 11 problems on this test. For each problem, write your answer in the space provided. You may use the backs of the pages for scratch calculations if you wish, but only the work in the spaces provided on the front of the pages will be graded. Problems A1-A5 are worth 6 points each. For these five problems, you do not need to show calculations or explain your reasoning unless requested. Also, no partial credit will be awarded for incorrect answers. Problems B1-B6 are worth 10 or 15 points each, as specified. For these six problems, you must show your work and/or explain your reasoning to receive any credit for a problem. Merely stating the answer is NOT sufficient. Partial credit will be awarded where appropriate. REMINDER: An answer CAN NOT be completely correct if it has the wrong units! G O O D L U C K!!!!!

Section A: Six points per problem. Encircle the correct answers. No partial credit will be awarded.

What happens to the brightness of the bulb when a piece of iron is inserted inside the inductor?

$The refracted rays (but not the reflected rays) are shown in each material.$ It is possible for your image to be (circle all that are possible): Real and upright Real and inverted Virtual and upright Virtual and inverted A4: A transmitting antenna is located at the

It is possible for your image to be (circle all that are possible): Real and upright Real and inverted Virtual and upright Virtual and inverted A4: A transmitting antenna is located at the

2 Section A: Six points per problem. Encircle the correct answers. No partial credit will be awarded. A1: An air-core inductor is connected in series with a light bulb, and this circuit is plugged into an electrical outlet. What happens to the brightness of the bulb when a piece of iron is inserted inside the inductor? Becomes brighter Stays the same Becomes dimmer A2: The drawing shows a ray of light traveling through three materials whose surfaces are parallel to each other. The refracted rays (but not the reflected rays) are shown in each material. Rank the materials according to their indices of refraction, from largest to smallest: abc acb bac bca cab cba A3: Suppose you stand in front of a spherical mirror (either concave or convex). It is possible for your image to be (circle all that are possible): Real and upright Real and inverted Virtual and upright Virtual and inverted A4: A transmitting antenna is located at the origin of an x, y, z axis system and broadcasts an electromagnetic wave whose electric field oscillates along the x axis. The wave travels along the +z axis. Wire loops in three different planes are available for use with an LC-tuned circuit to detect this wave. Which loop(s) will detect the wave? Loop in xy plane Loop in xz plane Loop in yz plane A5: The figures below show three polarizer/analyzer pairs. The incident light on each pair is unpolarized and has the same intensity. Rank the pairs according to the intensity of the transmitted light, from largest to smallest: abc acb bac bca cab cba

3 Section B: Must show your work. Partial credit will be awarded where appropriate. B1: (10 points) A 30.0 µf capacitor is connected across a 120 Hz generator. An inductor is then connected in parallel with the capacitor. What is the value of the inductance if the rms currents in the inductor and capacitor are equal? Inductance B2: (10 points) An object is located 7.9 cm in front of a mirror. The virtual image is located 5.5 cm away from the mirror and is smaller than the object. Find the focal length of the mirror. Focal length

B3: (10 points) A heat lamp emits infrared radiation with an rms electric field of E rms = 3100 N/C. The radiation falls on a person s leg over a circular area of radius 5.5 cm.

4 B3: (10 points) A heat lamp emits infrared radiation with an rms electric field of E rms = 3100 N/C. The radiation falls on a person s leg over a circular area of radius 5.5 cm. What is the average power delivered to the leg? Average power B4: (10 points) The drawing shows an optical fiber that consists of a core made of crown glass surrounded by a cladding made of fused quartz. A beam of light enters the fiber from air at an angle θ 1 with respect to the normal. (a) What is θ 1 if the light strikes the core-cladding interface at the critical angle θ c? (b) If a second beam of light enters the fiber at an angle 0.5 θ 1 with respect to the normal, will any of the second beam be refracted at the core-cladding interface or not? (Encircle your answer.) Angle θ 1 Second beam WILL WILL NOT have a refracted part at the core-cladding interface

5 B5 : (15 points) A 5.0 Ω resistor, a 9.5 µf capacitor, and a 21 mh inductor are connected in series with a 24.0 V generator. (a) At what frequency is the current through the circuit a maximum? (b) At that frequency, what is the rms voltage across the capacitor? Frequency Voltage B6: (15 points) A diverging lens (f = cm) is located 15.0 cm to the left of a converging lens (f = 31.0 cm). A 2.5 cm tall object stands to the left of the diverging lens, exactly at its focal point. (a) Determine the distance of the final image relative to the converging lens. (b) What is the height of the final image (including the proper algebraic sign)? Distance Image height

Geometric Optics. Ray Model. assume light travels in straight line uses rays to understand and predict reflection & refraction

$Geometric Optics. Ray Model. assume light travels in straight line uses rays to understand and predict reflection & refraction$ Geometric Optics Ray Model assume light travels in straight line uses rays to understand and predict reflection & refraction General Physics 2 Geometric Optics 1 Reflection Law of reflection the angle