Electromagnetic Waves Practice 2 Solution
Level 4
An object O is located at point P to the left of a converging lens, as shown in the figure. F
1 and F2 are the focal points of the lens.
1. If the focal length of the lens is 0.40 m and point P is 0.30 m to the left of the lens, where is the image of the
object located?
(A) 1.2 m to the left of the lens
(B) 0.17 m to the left of the lens
(C) At the lens
(D) 0.17 m to the right of the lens
(E) 1.2 m to the right of the lens
2. Which of the following characterizes the image when the object is in the position shown?
(A) Real, inverted, and smaller than the object
(B) Real, upright, and larger than the object
(C) Real, inverted, and larger than the object
(D) Virtual, upright, and larger than the object
(E) Virtual, upright, and smaller than the object
3.
A postage stamp is placed 30 centimeters to the left of a converging lens of focal length 60 centimeters. Where
is the image of the stamp located?
(A) 60 cm to the left of the lens (B) 20 cm to the left of the lens
(C) 20 cm to the right of the lens (D) 30 cm to the right of the lens
(E) 60 cm to the right of the lens
4. Which of the following is NOT possible for the images formed by the lens in the
accompanying figure?
A) real and inverted
B) real and smaller in size
C) real and larger in size
D) virtual and erect
E) virtual and smaller in size
The lens shown has thick in the center and thin on the outside which makes a converging lens. In
converging lenses, all of the real images are inverted and can be any size, but the virtual images
are formed in a magnifying lens scenario and are always larger and upright.
5. A physics student places an object 6.0 cm from a converging lens of focal length 9.0 cm. What is the magnitude
of the magnification of the image produced?
(A) 0.6 (B) 1.5 (C) 2.0 (D) 3.0 (E) 3.6
Using the math, 1/f = 1/do + 1/di, di = –18 … then M = – di / do … M = 3
6.
An illuminated object is placed 0.30 meter from a lens whose focal length is –0.15 meter. The image is
(A) inverted, real, and 0.30 meter from the lens on the opposite side from the object
(B) upright, virtual, and 0.30 meter from the lens on the opposite side from the object
(C) upright, real, and 0.10 meter from the lens on the same side as the object
(D) upright, virtual, and 0.10 meter from the lens on the same side as the object
7.
An object is in front of a convex lens, at a distance less than the focal length from the lens. Its image is
A) virtual and larger than the object.
B) real and smaller than the object.
C) virtual and smaller than the object.
D) real and larger than the object.
E) virtual and the same size as the object
A convex lens is a converging lens. When the object is in front of the focal point, it acts as a
magnifying glass.
8. A diverging lens produces an image of a real object. This image is
(A) virtual, larger than the object, and upright.
(B) virtual, smaller than the object, and upright.
(C) virtual, smaller than the object, and inverted.
(D) real, smaller than the object, and inverted.
(E) real, larger than the object, and inverted
Diverging lens always produces the same object type no matter what
Free Response
2002B4
2002B4. A thin converging lens of focal length 10 cm is used as a simple magnifier to examine an object A that is
held 6 cm from the lens.
(a) On the figure below, draw a ray diagram showing the position and size of the image formed.
(b) State whether the image is real or virtual. Explain your reasoning.
(c) Calculate the distance of the image from the center of the lens.
(d) Calculate the ratio of the image size to the object size.
Solution
1992B6
1992B6. A thin double convex lens of focal length f, = + 15 centimeters is located at the origin of the x-axis, as
shown above. An object of height 8 centimeters is placed 45 centimeters to the left of the lens.
a. On the figure below, draw a ray diagram to show the formation of the image by the lens. Clearly show
principal rays.
b. Calculate (do not measure) each of the following.
i. The position of the image formed by the lens
ii. The size of the image formed by the lens
c. Describe briefly what would happen to the image formed by the lens if the top half of the lens were
blocked so that no light could pass through.
1996B6 Solution
Level 5
1.
Answer:
Level 6
1.
A two slit interference experiment is performed with slit spacing a and wavelength A.
As the spacing is increased, holding A fixed, which of the following is true?
I. The width of the central maximum will decrease.
II. The width of the central maximum will increase.
III. There will be more interference fringes formed.
(A) I only (B) II only (C) III only (D) I and III (E) II and III
2.
A single slit with width w produces a diffraction pattern on a screen when illuminated with
light of a given wavelength. The entire experiment is then immersed in water with the same
light source. Which of the following is true?
(A) The diffraction pattern will contract.
(B) The diffraction pattern will expand.
(C) The diffraction pattern will be unchanged.
(D) The diffraction pattern will disappear.
(E) The central maximum becomes less intense than the secondary maxima.
3.
In an experiment to measure the wavelength of light using a double slit apparatus, it is found that the bright
fringes are too close together to easily count them. To increase only the spacing between the bright fringes, one
could
A) increase the slit width
B) decrease the slit width
C) increase the slit separation
D) decrease the slit separation
E) none of these
Based on m λ = dx / L we want to increase x. d is separation of slits and less d means more x
4.
If the intensity of a monochromatic ray of light is increased while the ray
is incident on a pair of narrow slits, the spacing between maxima in the
diffraction pattern will be
(A) increased
(B) decreased
(C) the same
(D) increased or decreased, depending on the frequency
(E) increased or decreased, depending on the slit separation
Free Response
Solution
2009B6
2009B6. In a classroom demonstration, a beam of coherent light of wavelength 550 nm is incident perpendicularly
onto a pair of slits. Each slit has a width w of 1.2 x 10–6 m, and the distance d between the centers of the slits is
1.8 x 10–5 m. The class observes light and dark fringes on a screen that is a distance L of 2.2 m from the slits. Your
notebook shows the following setup for the demonstration.
(a) Calculate the frequency of the light.
(b) Calculate the distance between two adjacent dark fringes on the screen.
Solution
2004B4
Solution
Level 6
B2009B5 Thin Film
A wide beam of white light is incident normal to the surface of a uniform oil film. An observer looking down at
the film sees green light that has maximum intensity at a wavelength of 5.2 x 10–7
the oil is 1.7.
m. The index of refraction of
(a) Calculate the speed at which the light travels within the film.
(b) Calculate the wavelength of the green light within the film.
(c) Calculate the minimum possible thickness of the film.
(d) The oil film now rests on a thick slab of glass with index of refraction 1.4, as shown in the figure below. A
light ray is incident on the film at the angle shown. On the figure, sketch the path of the refracted light ray
that passes through the film and the glass slab and exits into the air. Clearly show any bending of the ray at
each interface. You are NOT expected to calculate the sizes of any angles.
B2009B5 Solution