Physics 202 MWF 10:20 Spring 2004 (Ford)

Exan III Chapts. 23--26 in Cutnell and Johnson 6e

Multiple choice questions. Circle the correct answer. No work need be shown and no partial credit will be given.

(4 pts) 1. In an RLC series circuit the source voltage leads the current. The frequency f of the ac source

(a) is larger than the resonance frequency<------- Ans.
(b) is smaller than the resonance frequency
(c) is equal to the resonance frequency


(4 pts) 2. Consider the ac circuit shown in the sketch. The amplitude V₀ of the source voltage is 24 V. When the frequency f of the source is very large, the amplitude of the current through the source is



(a) 0
(b) 3 A<------- Ans.
(c) 5 A
(d) 8 A
(e) 11 A


(4 pts) 3. A spaceship emits electromagnetic waves with frequency 6.0× 10¹³ Hz. The speed of the waves is 3.0 × 10⁸ m/s. An observer on earth measures the waves to have wavelength 8.0 × 10^-6 m. Is the spaceship moving toward or away from earth?

(a) away from earth<------- Ans.
(b) toward earth


(4 pts) 4. Light traveling in water (n = 1.33) is incident on the flat surface of a piece of glass (n = 1.50) and refracts into the glass. As it enters the glass, the ray is bent

(a) toward the normal<------- Ans.
(b) away from the normal


(4 pts) 5. An object is to the left of a converging lens and the image is upright. Where is the image?

(a) to the left of the lens<------- Ans.
(b) to the right of the lens


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

(12 pts) 6. Unpolarized light of intensity 220 W/m² and traveling horizontally is incident on two polarizers. The axis of the first polarizer is at an angle of 22° clockwise from the vertical and the axis of the second polarizer is at an angle of 78° clockwise from the vertical. What is the intensity of the light after it has passed through the second polarizer?



Ans. _____34.4 W/m²___


(16 pts) 7. The cylindrical beam of light from a laser has wavelength 600 nm and a cross sectional area 5.0 × 10^-4 m². A 3.0 m length of the beam contains 8.0 × 10^-8 J of energy.

a) What is the intensity of the light?

Ans. _____1.60 × 10⁴ W/m²_______

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

Ans. _____8.0 W____


(18 pts) 8. An object 2 mm tall is 30 cm to the left of a convex mirror that has a radius of curvature of 20 cm.

a) Is the image real or virtual?

Ans. ____virtual______

b) How far is the image from the mirror?

Ans. _____7.5 cm_______

c) Is the image upright or inverted?

Ans. ____upright_____

d) What is the height of the image?

Ans._____0.5 mm______


(16 pts) 9. A nearsighted person wears contacts to correct for a far point that is only 400 cm from his eye. The near point of his unaided eye is 30.0 cm from his eyes.

a) What is the focal length of the contact lens that corrects his far vision?

Ans. ____-400 cm_____

b) If he does not remove the lens when reading, how close to his eye can he hold a book and see it clearly?

Ans. ______32.4 cm____


(18 pts) 10. Consider the ac circuit shown in the sketch. The amplitude of the source voltage is V₀ = 141 V and the frequency of the source is f = 50 Hz. The amplitude of the voltage across the resistor is 64 V. The amplitude of the current in the circuit is I₀ = 2.0 A.



a) What is the amplitude of the voltage across the inductor?

Ans. _____126 V___

b) What is the average power delivered by the source?

Ans. _____64 W____

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

Ans. _____leads______