Physics 202 MWF 10:20 Spring 1997 (Ford)
Exam IV Chapts. 36-39 in SZY College Physics 7e


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


(17 pts) 1. Consider the image of your face in a spherical mirror. It is desired that the image be virtual, erect, and 1.5 times the size of the object. The object (your face) is 30 cm from the vertex of the mirror.

a) Calculate the radius of curvature of the mirror that will produce such an image.

Ans. _________________

b) Is the mirror convex (negative R) or concave (positive R)?

Ans. _____________________


(16 pts) 2. A flat piece of glass, refractive index 1.50, is placed on the surface of water, refractive index 1.33. Above the glass is air, refractive index 1.00. A ray of light traveling in the water is incident on the bottom surface of the glass.

a) If the wavelength of the light in the glass is = 400 × 10^-9 m, what is its wavelength in the water?

Ans. ___________________

b) Is the refracted ray, that passes from the water into the glass, bent toward or away from the normal?

Ans. _____________

c) What is the largest value of the angle of incidence at the water-glass interface for which there will still be some light refracted into the air at the glass-air interface? Ans. _____________________


(14 pts) 3.

a) Light traveling in the +z-direction and with intensity I₀ is polarized along the y-axis. It is passed through two polarizers, that have their polarizing axes oriented as shown in the sketch. The axis of the first poalrizer that the light passes through, polarizer #1, is oriented at 30° from the y-axis, and the axis of the second polarizer that the light passes through, polarizer #2, is aligned along the x-axis. In terms of I₀, what is the intensity of the light after it has passed each polarizer?


Ans. after polarizer #1 ___________________

after polarizer #2 ________________

b) If polarizer #1 is removed, what is the intensity of the light passed by polarizer #2?

Ans. _________________


(16 pts) 4. The left-hand end of a glass rod is ground to a concave surface with a radius of curvature that has magnitude |R| = 12 cm. The refractive index of the glass is 1.50. A fly is embedded within the glass on the axis of the rod, 18 cm to the right of the vertex of the spherical surface.

a) Where is the image of the fly when viewed by a person in the air to the left of the rod? (That is, how far is the image from the vertex of the spherical surface?)

Ans. __________________

b) Is the image real or virtual?

Ans. ___________________


(17 pts) 5. Coherent light with wavelength = 600 nm in air is incident on a soap film (n = 1.33). What is the smallest thickness of the soap film (not counting zero thickness) for which there will be destructive interference between the light reflected at the top and bottom surfaces of the film? There is air on both sides of the film.

Ans. ______________________


(20 pts) 6. 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. ___________________

b) Is the final image real or virtual? Ans. __________________

c) Is the final image erect or inverted? Ans. __________________

d) What is the height of the final image? Ans. ___________________