Physics 6C Midterm Practice Questions
1.
A 5-mm tall object is placed 2 cm away from a lens, and an upright image is formed that
is 5 cm tall. What is the focal length of the lens?
a)
b)
c)
d)
-2.2 cm
-5.0 mm
+2.2 cm
+3.3 cm
2.
A beam of light with wavelength 600 nm falls on a single slit of width 0.015 mm. The
resulting diffraction pattern is viewed on a screen 10 m away. Find the distance from the
center of the pattern to the center of the second bright fringe.
a)
b)
c)
d)
10 cm
60 cm
80 cm
100 cm
3.
An oil film floats on water. The refractive index of the oil is 1.4 and the index for water
is 1.33. The film appears blue because it reflects light with wavelength 400 nm very
well. Calculate the minimum thickness of the oil film.
a)
b)
c)
d)
71 nm
100 nm
143 nm
200 nm
4.
A light ray traveling in air enters a glass plate with index of refraction 1.62. The ray
enters the glass at an angle of 39° to the normal. What angle does the ray make with the
normal when it is in the glass?
a) 23°
b) 29°
c) 39°
d) the ray is completely reflected back into the air
5.
A light ray in glass (index 1.62) is incident on an glass/air interface at an angle of 39° to
the normal. What angle does the ray make with the normal when it leaves the glass and
enters the air?
a) 23°
b) 29°
c) 39°
d) the ray is completely reflected back into the glass
6.
Unpolarized sunlight is incident on a Polaroid filter. The light that is transmitted then
encounters another filter whose transmission axis is at an angle of 34° to the first one.
What percentage of the original sunlight intensity is transmitted through the second filter?
a) 0%
b) 34%
c) 68%
d) 83%
7.
An object is 4m away from a wall. You are to use a concave mirror to project an image
of the object on the wall, with the image 2.25 times the size of the object. What should
the radius of curvature of the mirror be?
a) 1.1m
b) 2.2m
c) 4.4m
d) 5.5m
8.
A double-slit experiment is performed with light of wavelength of 500 nm, and the first
dark fringe appears at a distance of 4cm from the central bright maximum. If this
experiment is now performed with the same setup, but underwater, how far from center
will the first dark fringe be? Assume the index of refraction of water is 1.33.
a) 2 cm
b) 3 cm
c) 4 cm
d) 5 cm
9.
Quincy Magoo is a man with poor eyesight. The farthest object he can see clearly is only
15 cm away. Find the lens power (in Diopters) that will correct his nearsightedness so
that distant objects will appear clear to him.
a) -15.0
b) -6.67
c) -1.50
d) +1.50
10.
At a point in space an electromagnetic wave is propagating in the negative x direction. At
a certain instant, the magnetic field of the wave at this point is in the positive y direction.
At this point and this instant, the electric field of the wave is
a)
b)
c)
d)
in the positive z direction
in the positive x direction
in the negative y direction
in the negative z direction
11.
A certain part of the electromagnetic spectrum ranges from 200nm to 400nm. What is the
highest frequency associated with this portion of the spectrum? (1nm= 10-9m)
a) 1.50 x 1014 Hz
b) 7.50 x 1015 Hz
c) 1.50 x 1015 Hz
d) 7.50 x 1014 Hz
12.
Which of the following is the correct order of the electromagnetic spectrum from low to
high wavelength?
a) Radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma-rays
b) Radio waves, microwaves, infrared, visible, ultraviolet, gamma-rays, x-rays
c) Gamma-rays, x-rays, ultraviolet, visible, infrared, microwaves, radio waves
d) X-Rays, ultraviolet, gamma-rays, radio waves, visible, infrared, microwaves
13.
If a double-concave lens that is normally used in air is placed in water instead, does the
focal length increase, decrease, or stay the same?
a) Decrease
b) Stay the same
c) Increase
d) Cannot be determined from the information given
14.
A light ray is in water is incident at an angle of 22.8° on an oil film with thickness 560
nm and index of refraction 1.45. Does the light ray that is transmitted into the oil bend
toward or away from the normal? Assume that the index of refraction of water is 1.33.
a) Toward
b) Away
c) The ray does not bend at all.
d) The ray is completely reflected.
15.
A 3-cm tall object is placed 50 cm away from a diverging lens of focal length 25 cm.
Describe the image.
a) The image is real, 1.5-cm tall, 25.0 cm on the same side as the object.
b) The image is virtual, 1-cm tall, 16.7 cm on the same side as the object.
c) The image is real, 3-cm tall, 50.0 cm on the other side of the lens.
d) The image is virtual, 1-cm tall, 16.7 cm on the other side of the lens.
16.
Two telescopes are to be placed in orbit. One telescope is designed to be used with
visible light of wavelength 500nm, while the second telescope is designed to be used with
infrared light of wavelength 2000nm. In order that both telescopes have the same
resolution, the mirror of the infrared telescope must have
a)
b)
c)
d)
1/4 the diameter of the visible-light telescope’s mirror
2 times the diameter of the visible-light telescope’s mirror
4 times the diameter of the visible-light telescope’s mirror
16 times the diameter of the visible-light telescope’s mirror
Answers:
1c; 2d; 3a; 4a; 5d; 6b; 7c; 8b; 9b; 10a; 11c; 12c; 13c; 14a; 15b; 16c