In-Class Practice Exam 2
Geometric & Physical Optics
Problem 1
Light refracts from material 1 into a thin layer of material 2, crosses that layer, and then
is incident at the critical angle on the interface between
materials 2 and 3, and refracts into material 4.
a. What is the angle θ and the angle of refraction into
material 4?
b. Draw an accurate diagram of the situation.
c. If θ is decreased, is there refraction of light into
material 3?
Problem 2
The radii of curvature of the surfaces of a thin converging meniscus lens (n = 1.60) are
R1 = +12.0 cm and R2 = +28.0 cm.
a. Compute the position and size of the image of an object in the form of an arrow 5.00
mm tall and 45.0 cm to the left of the lens. Is the real or virtual, erect or inverted,
enlarged or reduced?
b. A converging mirror, of radius 70 cm, is placed 228 cm to the right of the converging
lens. Find the position and size of the final image. Is the real or virtual, erect or
inverted, enlarged or reduced?
c. Draw a ray diagram showing the location of the final image
Review-1
Problem 3
Two radio antennas radiating in phase are located at points A and B, 200 m
apart. The radio waves have a frequency of 5.80×106 Hz.
a. At what distance from B will there be the first destructive interference
location along the BC line?
b. What is the relative intensity at this point x = 100 m from point B? (i) If this
point is closer to a “dark or bright” fringe, what is the fringe number? If not, is it closer
to a dark or a bright fringe? (ii) Draw a sketch of the interference pattern and show
where this point x is located.
Problem 4
In the single-slit diffraction experiment, let the wavelength of the light be 500 nm, the slit
width be 6 m, and the viewing screen be at distance 3.00 m.
a. How many minimas does this diffraction pattern have?
b. What is the approximate location and relative intensity of the second diffraction
maxima?
Review-2
Problem 6
Use short concise sentences to answer the following questions using physics principles.
Make sure to explain your reasoning for each answer.
a. Why is glass transparent and walls no transparent?
b. Where must the film be placed if a camera lens is to make a sharp image of an
object far away?
c. What type of optical “thing” produces this image? How far is the object from the
“thing” (answer in terms of focal length f and Center of curvature C)? Describe the
image characteristics?
d. The speed and wavelength of, say, red light that we see in air are reduced when the
light passes into water. Would that light then appear to be another color – blue,
perhaps – if you viewed it from under the water surface?
e. The sound waves used predominantly in human speech have wavelengths in the
range from 1.0 and 3.0 meters. Using the ideas of diffraction, explain how it is
possible to hear a person’s voice even when they are facing away from you.
Review-3