Physics 202 MWF 10:20 Spring 2003 (Ford)

Exan III Chapts. 23--26 in Cutnell and Johnson 4e

Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.

(14 pts) 1. An ac series circuit contains an ac source with rms voltage 140 V, a resistor R = 70 , a capacitor C = 5.0 × 10^-6 F, and an inductor L =0.020 H. If the source is operated at the resonance frequency of the circuit, what is the average power the source provides to the circuit?

Ans. ____280 W____


(16 pts) 2. An ac series circuit contains an ac source with voltage amplitude 220 V and angular frequency 5000 rad/s, a resistor R, and an inductor with L = 0.040 H. The current amplitude in the circuit is 0.500 A.

a) Does the source voltage lag or lead the current?

Ans. ____leads___

b) What is the resistance R of the resistor?

Ans._____392 _____

c) What is the average power supplied by the source?

Ans._____49 W___


(12 pts) 3. A person's eye can't focus on objects closer than 60.0 cm or farther than 2.80 m from the eye.

a) What is the focal length of the contact lens that will allow the person to focus on very distant objects?

Ans. ____-280 cm___

b) When the person is wearing the contact lens from part (a), what is the closest distance at which he can clearly see objects?

Ans. _____76.4 cm____


(12 pts) 4. Unpolarized light of intensity S₀ is incident on three polarizers. The axis of the first polarizer is vertical, the axis of the second polarizer is at 33° counterclockwise from the vertical and the axis of the third polarizer is 57° counterclockwise from the vertical. The intensity of the light after it has passed through all three polarizers is 300 W/m². What was the incident intensity S₀?

Ans. ____1020 W/m²____


(12 pts) 5. Energy is distributed uniformly in a laser beam of cross-sectional area 0.0016 m². The energy in a 0.400-m length of the beam is 1.2 × 10^-6 J.

a) What is the intensity of the laser beam?

Ans. ____5.62 × 10⁵ W/m²___

b) What is the average power output of the laser?

Ans. ____900 W___


(16 pts) 6. A small candle is placed to the left of a concave mirror whose radius of curvature is 40 cm. The image formed by the mirror is upright and its height is four times the height of the object.

a) Is the image real or virtual?

Ans. ____virtual___

b) How far is the candle from the mirror?

Ans. ___15 cm_____


(16 pts) 7. An object 2.0 mm tall is placed 20 cm to the left of a converging lens which is in turn 12 cm to the left of a diverging lens. The converging lens has focal length f₁ = +10 cm and the diverging lens has f₂ = -10 cm.

a) How far is the final image from the diverging lens? Is it to the left or to the right of this lens?

Ans. ____40 cm to right___

b) Is the final image real or virtual?

Ans. _____real____

c) Is the final image upright or inverted, with respect to the original object?

Ans. ___inverted____

d) What is the height of the final image?

Ans. ___10.0 mm______