True-false questions are worth 2 points each, three-choice multiple
choice questions are worth 3 points each, five-choice multiple choice
questions are worth 6 points each. The maximum possible score is 94.
The exam period was 75 minutes; the mean score was 67.1; the median was
66. Click here to see page1
page3 with the exam.
Some helpful information:
• A reminder about prefixes: p (pico) = 10-12; n
(nano) = 10-9; μ (micro) = 10-6; m (milli) =
10-3; k (kilo) = 10+3; M or Meg (mega) =
10+6; G or Gig (giga) = 10+9.
Unpolarized light with average intensity I = 200 W/m2
is incident upon a pair of polarizers, the first with transmission axis
oriented 68° above the x-axis, and the second with
transmission axis oriented 24° above the x-axis.
What is the peak value of the magnetic field in the light
before it strikes the first polarizer?
(a) 9.2 × 10-7 T
(b) 1.3 × 10-6 T
(c) 1.8 × 10-6 T
(a) 23 W/m2
(b) 33 W/m2
(c) 52 W/m2
(d) 68 W/m2
(e) 72 W/m2
(a) The intensity of light emerging from the second polarizer will either be
unaffected by the additional polarizer, or reduced because of it.
(b) The intensity of light emerging from the second polarizer might be reduced,
unaffected, or increased because of the presence of the additional polarizer.
A real object is held 32 cm in front of a mirror. You will not be
told the location of the image it forms, but you are told that the
magnification under these circumstances is 0.7 (note that this
magnification is positive).
Is the image formed real or virtual?
(a) -75 cm
(b) -13 cm
(c) 13 cm
(d) 32 cm
(e) 75 cm
(a) Yes, you could use these glasses as magnifiers.
(b) No, you could not use these glasses as magnifiers.
(a) -41 cm
(b) -15 cm
(c) 15 cm
(d) 41 cm
(e) 48 cm
In order to project a clear image onto the screen, how far should the
screen be from the second lens? Solve for x.
(a) 3.5 cm
(b) 5.8 cm
(c) 7.2 cm
(e) There is no value of x which would produce a clear image on the screen.
(a) 420 nm
(b) 540 nm
(c) 670 nm
(d) 840 nm
(e) 1080 nm
What values of n would guarantee that all the
horizontal light is reflected back into the glass? Find the greatest
range of values that work.
(a) n > 1.33
(b) n > 1.41
(c) n > 1.88
(d) n < 1.41
(e) No value of n would guarantee this.
A thin film of oil (index of refraction 1.52) is poured on top of water
(index of refraction 1.33). The oil is illuminated from the air above
it by monochromatic light.
What smallest thickness t of oil would cause orange light
(λ = 590 nm) to be most strongly reflected?
(a) 97 nm
(b) 110 nm
(c) 194 nm
(d) 210 nm
(e) 220 nm
Do we find a bright spot or a dark spot at the edge of the oil (where
the thickness of the oil layer approaches zero)?
(a) t + 97 nm
(b) t + 194 nm
(c) t + 295 nm
A diffraction grating has 3000 lines (slits) per cm.
When illuminated by green light of wavelength 540 nm, at which of
these angles is the second-order maximum detected?
(T) True, a violet bright spot coincides with the fourth-order green maximum.
(F) False, no violet bright spot overlaps the fourth-order green maximum.
(a) 130 m
(b) 1300 m
(c) 13 km
Compare what happens with the barrier (creating two slits) versus
without the barrier (a single wide slit).
(a) Without the barrier, there is a bright spot at
θ = 0, which disappears when the barrier is inserted.
(b) With the barrier, there is a bright spot at θ = 0, which
disappears when the barrier is removed.
(c) There is always a bright spot at θ = 0, regardless of
whether the barrier is present or not.
(a) The final image is real, enlarged, and upright.
(b) The final image is virtual, enlarged, and inverted.
(c) The final image is real, enlarged, and inverted.
(d) The final image is virtual, reduced, and inverted.
(e) The final image is real, reduced, and inverted.
(a) The transmission axis of the polarizer is horizontal.
(b) The transmission axis of the polarizer is vertical.
This diagram shows two principal rays after having been reflected by
a concave mirror. (The principal ray which passes through the center of
curvature is not shown.) The two upright arrows are not part of
the diagram but they are drawn to the same scale as the diagram.
You should assume that these rays of light started, before
reflecting, at the top of a single real object; the bottom of that
object rests on the principal axis (the dashed line).
One of those two arrows has the same height as the object in this
problem. Which one?
(a) The image is virtual because the object is to the left of the focal point.
(b) The image is real because the object is to the left of the focal point.
(c) The object is at the focal point.
(d) The image is virtual because the object is to the right of the focal point.
(e) The image is real because the object is to the right of the focal point.