Physics 202 MWF 10:20 Spring 2000 (Ford)

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

(8 pts) 1. An object is placed to the left of a diverging lens as shown in the sketch. The focal points F on either side of the lens are shown. On the diagram draw at least two principal rays and show the location of the image.



Is the image real or virtual? Ans. _____virtual_____

Is the image upright or inverted? Ans. _____upright____


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


(3 pts) 2. Consider the ac circuit shown in the sketch. When the frequency of the ac generator is very large, the current amplitude through the generator is

a) zero
b) 2 A
c) 3 A
d) 4 A
e) 6 A <---------- answer
f) infinite


(3 pts) 3. Consider the series RCL circuit shown in the sketch. The frequency f of the ac generator is larger than the resonant frequency of the circuit. Which statement is correct:

a) the soruce voltage lags the current
b) the source voltage leads the current <---------- answer
c) the source voltage is in phase with the current


(3 pts) 4. You observe the light emitted from a moving source. The wavelength you observe from the moving source is larger than the wavelength emitted by the source. (By ``wavelength emitted by the source'' we mean the wavelength you would observe if the source were at rest relative to you.) The source is

a) approaching you
b) moving away from you <---------- answer


(3 pts) 5. An object is placed to the left of a thin lens. The image formed by the lens is upright. The image is

a) real
b) virtual <---------- answer


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


(18 pts) 6. A concave mirror with a radius of curvature 40 cm forms an image of a 2 mm tall object that is to the left of the mirror. The image is 8 mm tall and is upright.

a) What is the distance of the object from the mirror vertex?

Ans. ___15 cm____

b) What is the distance of the image from the mirror vertex? Is the image real or virtual?

Ans. ___- 60 cm_____

Ans. ___virtual_____


(8 pts) 7. Light is incident from the left on two polarizing filters, 1 and 2. The transmission axis of filter 1 makes an angle = 37° with respect to the vertical and the axis of filter 2 is vertical. If the incident light is unpolarized and has intensity 50 W/m², what is the intensity of the light after it has passed through the second filter?



Ans. ___15.9 W/m²______


(12 pts) 8. An electromagnetic wave from a radio station passes perpendicularly through an open window that has area 0.50 m². At the window the electric field of the wave has rms value 0.020 V/m. How much energy does this wave carry through the window during a 30-second commecial?

Ans. ___1.59 × 10^-5 J_____


(20 pts) 9. Consider the series RCL circuit shown in the sketch. R = 300 , L = 0.40 H and C = 6.0 × 10^-8 F. When the ac generator operates at the resonant frequency, the current amplitude in the circuit is 0.50 A.

a) What is the voltage amplitude of the generator?

Ans. ____150 V____

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

Ans. ____1291 V____

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

Ans. ____37.5 W____


(22 pts) 10. 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 f₁ = +10 cm and the diverging lens has f₂ = -10 cm.



a) How far is the final image from the object?

Ans. ____72 cm to right_____

b) Is the final image real or virtual?

Ans. ___real____

c) Is the final image upright or inverted?

Ans. ____inverted____

d) What is the height of the final image?

Ans. _____10.0 mm____