TIME OF COMPLETION___________NAME____SOLUTION_________________________

 

 

                                           DEPARTMENT OF NATURAL SCIENCES

 

PHYS 1112, Exam 3                                                                                                             Section 1

Version 1                                                                                                                       April 23, 2003

Total Weight: 100 points

 

1.         Check your examination for completeness prior to starting.  There are a total of ten (10) problems on eight (8) pages.

 

2.         Authorized references include your calculator with calculator handbook, and the Reference Data Pamphlet  (provided by your instructor).

 

3.         You will have 80 minutes to complete the examination.

 

4.         The total weight of the examination is 100 points.

 

5.         There are six (6) multiple choice and four (4) calculation problems. Work all problems.  Show all work; partial credit will be given for correct work shown.

 

6.         If you have any questions during the examination, see your instructor who will

be located in the classroom.

 

7.         Start:                11:30 a.m.

Stop:                12:50 a.m

 

 

 

               PROBLEM

 

                 POINTS

 

                 CREDIT

 

                     1-6

 

                      30

 

 

 

                       7

 

                      20

 

 

 

8

 

                      15

 

 

 

                       9

 

                      20

 

 

 

                      10

 

                      15

 

 

 

                 TOTAL

 

                     100

 

 

 

 

 

           PERCENTAGE

 

 

 

CIRCLE THE SINGLE BEST ANSWER FOR ALL MULTIPLE CHOICE QUESTIONS. IN MULTIPLE CHOICE QUESTIONS WHICH REQUIRE A CALCULATION SHOW WORK FOR PARTIAL CREDIT.

 

 

 

1.  A monochromatic (single frequency, single wavelength) light ray in air (n = 1.00) enters a glass prism (n = 1.50). In the glass prism

 

    1. Both the frequency and the wavelength are the same as in air.

 

    1. The frequency is the same, but the wavelength is greater than in air.

(5)

    1. The frequency is the same, but the wavelength is smaller than in air.                   (ln=l/n)

 

    1. The wavelength is the same, but the frequency is greater than in air.

 

 

 

 

  1. If you stand closer to a concave mirror than a distance of one focal length, the image you see is

 

    1. Real and inverted.

 

    1. Real and upright.

(5)

    1. Virtual and inverted.

 

    1. Virtual and upright.

 

 

  1. Suppose that you carry out the analysis of a mirror system and find that the image distance is negative. This finding tells you that the image is

 

    1. Magnified.

 

    1. Inverted.

(5)

    1. Black and white.

 

    1. Virtual.

 

 

  1. Coherent lightwaves never arise from

 

    1. Two pinholes.

 

    1. Two lasers.

(5)

    1. Two light bulbs.

 

    1. Two slits.

 

 

 

 

  1. A bird is sitting on a perch peering into a small convex mirror in its cage. The image it sees is

 

    1. Always real.

 

    1.  Always virtual.

(5)

    1. Always magnified.

 

    1. Always inverted.

 

 

6. Of the following statements about the speed of various colors of light in glass, which one is true?

 

    1. All colors of light have the same speed in glass.

 

    1. Violet has the highest speed, red the lowest.

(5)

    1. Red has the highest speed, violet the lowest.

 

    1. Green has the highest speed, red and violet the lowest.

 

 

 

 

 

 

 

 

 

  1. A pretty but deadly 75.0 cm long coral snake (Micrurus fulvius) is stretched out along the principal axis of a convex mirror of radius of curvature 150 cm. Its head is 50.0 cm from the mirror vertex with its tail further away.

 

    1. Determine the location of the image of the snake’s head.

f = - R/2 = -75.0 cm

p = 50.0 cm

1/p + 1/q = 1/f

1/q = 1/f – 1/p

1/q = 1/(-75.0 cm) – 1/(50.0 cm)

q = -30.0 cm

 

    1. Determine the location of the image of the snake’s tail.

 

f = - R/2 = -75.0 cm

p = 125 cm

1/p + 1/q = 1/f

1/q = 1/f – 1/p

1/q = 1/(-75.0 cm) – 1/(125 cm)

q = -46.9 cm

    1. Is the length of the image of the shake longer or shorter than its actual length?

 

L” = 46.9 cm – 30.0 cm = 16.9 cm

Shorter!

    1. Is the image of the snake real or virtual?

 

Virtual, image distances are negative.

 

  1. A bi-concave lens of index of refraction 1.45 has radii of curvature of 30.0 and 45.0 cm.

 

    1. Find the focal length of the lens. (Hint: radius of curvature is positive if the center of curvature is located in back of the lens and is negative if the center of curvature is located in front of the lens.)

1/f = (n - 1) (1/R1 – 1/R2)

R1 = -30.0 cm

R2 = -45.0 cm

1/f = (1.45 - 1) (1/(-30.0 cm) – 1/(45.0 cm))

f = -40.0 cm

    1. An object is located 80.0 cm to the left of the lens. What is the location of the image?

 

 

p = 80.0 cm

1/p + 1/q = 1/f

1/q = 1/f – 1/p

1/q = 1/(-40.0 cm) – 1/(80.0 cm)

q = -26.7 cm

    1. Find the lateral magnification of the lens.

 

M = -q/p

M = - (-26.7 cm)/(80.0 cm) = 0.334

 

    1. Is the image real or virtual, upright or inverted, enlarged or reduced in size?

 

Virtual (q < 0), upright (M >0), and reduced (|M| < 1).

 

    1. Draw the ray diagram to verify your answers.

 

 

 

 

  1. Two converging lenses, each of focal length 10.0 cm are separated by 35.0 cm. An object is 20.0 cm to the left of the first lens.

 

    1. Find the position of the final image.

1/p1 + 1/q1 = 1/f1

1/q1 = 1/f1 – 1/p1

1/q1= 1/(10.0 cm) – 1/(20.0 cm)

q1 = 20.0 cm

 

p2 =  35.0 cm - q1 = 15.0 cm

 

1/p2 + 1/q2 = 1/f2

1/q2 = 1/f2 – 1/p2

1/q2= 1/(10.0 cm) – 1/(15.0 cm)

q1 = 30.0 cm

 

    1. What is the overall magnification of the image?

 

M1 = -q1/p1

M1 = - (20.0 cm)/(20.0 cm) = -1.00

 

M2 = -q2/p2

M2 = - (30.0 cm)/(15.0 cm) = -2.00

 

M = M1 M2 = 2.00

 

    1. Is the image real or virtual, upright or inverted, enlarged or reduced in size?

 

Real (q > 0), upright (M >0), and enlarged (|M| >

  1.  Light of wavelength 633 nm from a helium-neon laser is shone normally on a plane containing two slits. The first interference maximum is 82.0 cm away from the central maximum on the screen 12.0 m away.

 

 

    1. What is the separation of the slits?

 

y = lLm/d                          

 

y1 = lL/d                  (m = 1)

 

d = lL/y1

 

d = (633 x 10-9 m)(12.0 m)/ (0.82 m) = 9.26 x 10-6 m

 

    1. Does this maximum correspond to a constructive or destructive interference?

Constructive interference.