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Principles of Physics a Calculus Based Text

Raymond A. Serway, John W. Jewett, Jr.

Chapter 26

Image Formation by Mirrors and Lenses - all with Video Answers

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Chapter Questions

11:51

Problem 1

Determine the minimum height of a vertical flat mirror in which a person $178 \mathrm{cm}$ tall can see his or her full image. Suggestion: Drawing a ray diagram would be helpful.

Matthew Kegley
Matthew Kegley
Numerade Educator
07:18

Problem 2

(a) Does your bathroom mirror show you older or younger than you actually are? (b) Compute an order-of-magnitude estimate for the age difference based on data you specify.

Matthew Kegley
Matthew Kegley
Numerade Educator
03:41

Problem 3

A periscope (Fig. P26.3) is useful for viewing objects that cannot be seen directly. It can be used in submarines and when watching golf matches or parades from behind a crowd of people. Suppose the object is a distance $p_{1}$ from the upper mirror and the centers of the two flat mirrors are separated by a distance $h$. (a) What is the distance of the final image from the lower mirror? (b) Is the final image real or virtual? (c) Is it upright or inverted? (d) What is its magnification? (e) Does it appear to be left-right reversed?

Vishal Gupta
Vishal Gupta
Numerade Educator
12:37

Problem 4

In a choir practice room, two parallel walls are $5.30 \mathrm{m}$ apart. The singers stand against the north wall. The organist faces the south wall, sitting $0.800 \mathrm{m}$ away from it. To enable her to see the choir, a flat mirror $0.600 \mathrm{m}$ wide is mounted on the south wall, straight in front of her. What width of the north wall can the organist see? Suggestion: Draw a top-view diagram to justify your answer.

Matthew Kegley
Matthew Kegley
Numerade Educator
10:36

Problem 5

A person walks into a room that has two flat mirrors on opposite walls. The mirrors produce multiple images of the person. Consider only the images formed in the mirror on the left. When the person is 2.00 m from the mirror on the left wall and $4.00 \mathrm{m}$ from the mirror on the right wall, find the distance from the person to the first three images seen in the mirror on the left wall.

Matthew Kegley
Matthew Kegley
Numerade Educator
00:30

Problem 6

Two flat mirrors have their reflecting surfaces facing each other, with the edge of one mirror in contact with an edge of the other, so that the angle between the mirrors is $\alpha$. When an object is placed between the mirrors, a number of images are formed. In general, if the angle $\alpha$ is such that $n \alpha=360^{\circ},$ where $n$ is an integer, the number of images formed is $n-1 .$ Graphically, find all the image positions for the case $n=6$ when a point object is between the mirrors (but not on the angle bisector).

Keshav Singh
Keshav Singh
Numerade Educator
13:28

Problem 7

A convex spherical mirror has a radius of curvature of magnitude $40.0 \mathrm{cm} .$ Determine the position of the virtual image and the magnification for object distances of $30.0 \mathrm{cm}$ and (b) $60.0 \mathrm{cm} .$ (c) Are the images in parts (a) and (b) upright or inverted?

Matthew Kegley
Matthew Kegley
Numerade Educator
06:10

Problem 8

A dentist uses a spherical mirror to examine a tooth. The tooth is $1.00 \mathrm{cm}$ in front of the mirror, and the image is formed $10.0 \mathrm{cm}$ behind the mirror. Determine (a) the mirror's radius of curvature and (b) the magnification of the image.

Matthew Kegley
Matthew Kegley
Numerade Educator
08:35

Problem 9

A large hall in a museum has a niche in one wall. On the floor plan, the niche appears as a semicircular indentation of radius $2.50 \mathrm{m}$. A tourist stands on the centerline of the niche, $2.00 \mathrm{m}$ out from its deepest point, and whispers "Hello." Where is the sound concentrated after reflection from the niche?

Matthew Kegley
Matthew Kegley
Numerade Educator
05:41

Problem 10

Why is the following situation impossible? At a blind corner in an outdoor shopping mall, a convex mirror is mounted so pedestrians can see around the corner before arriving there and bumping into someone traveling in the perpendicular direction. The installers of the mirror failed to take into account the position of the Sun, and the mirror focuses the Sun's rays on a nearby bush and sets it on fire.

Matthew Kegley
Matthew Kegley
Numerade Educator
08:39

Problem 11

A concave spherical mirror has a radius of curvature of magnitude $20.0 \mathrm{cm} .$ (a) Find the location of the image for object distances of (i) $40.0 \mathrm{cm},$ (ii) $20.0 \mathrm{cm},$ and (iii) $10.0 \mathrm{cm}$ For each case, state whether the image is (b) real or virtual and (c) upright or inverted. (d) Find the magnification in each case.

Vishal Gupta
Vishal Gupta
Numerade Educator
06:46

Problem 12

A ball is dropped at $t=0$ from rest $3.00 \mathrm{m}$ directly above the vertex of a concave spherical mirror that has a radius of curvature of magnitude $1.00 \mathrm{m}$ and lies in a horizontal plane. (a) Describe the motion of the ball's image in the mirror. (b) At what instant or instants do the ball and its image coincide?

Vishal Gupta
Vishal Gupta
Numerade Educator
06:00

Problem 13

(a) A concave spherical mirror forms an inverted image 4.00 times larger than the object. Assuming the distance between object and image is $0.600 \mathrm{m}$, find the focal length of the mirror. (b) What If ? Suppose the mirror is convex. The distance between the image and the object is the same as in part (a), but the image is 0.500 the size of the object. Determine the focal length of the mirror.

Sheh Lit Chang
Sheh Lit Chang
University of Washington
09:12

Problem 14

(a) A concave spherical mirror forms an inverted image different in size from the object by a factor $a>1 .$ The distance between object and image is $d$. Find the focal length of the mirror. (b) What If? Suppose the mirror is convex, an upright image is formed, and $a<1 .$ Determine the focal length of the mirror.

JR
Jeff Radloff
Numerade Educator
01:57

Problem 15

To fit a contact lens to a patient's eye, a keratometer can be used to measure the curvature of the eye's front surface, the cornea. This instrument places an illuminated object of known size at a known distance $p$ from the cornea. The cornea reflects some light from the object, forming an image of the object. The magnification $M$ of the image is measured by using a small viewing telescope that allows comparison of the image formed by the cornea with a second calibrated image projected into the field of view by a prism arrangement. Determine the radius of curvature of the cornea for the case $p=30.0 \mathrm{cm}$ and M=0.013 0.

Keshav Singh
Keshav Singh
Numerade Educator
01:31

Problem 16

A concave mirror has a radius of curvature of $60.0 \mathrm{cm} .$ Calculate the image position and magnification of an object placed in front of the mirror at distances of (a) $90.0 \mathrm{cm}$ and (b) $20.0 \mathrm{cm} .$ (c) Draw ray diagrams to obtain the image characteristics in each case.

Mayukh Banik
Mayukh Banik
Numerade Educator
03:18

Problem 17

An object $10.0 \mathrm{cm}$ tall is placed at the zero mark of a meter-stick. A spherical mirror located at some point on the meter-stick creates an image of the object that is upright, $4.00 \mathrm{cm}$ tall, and located at the 42.0 -cm mark of the meter-stick. Is the mirror convex or concave? (b) Where is the mirror? (c) What is the mirror's focal length?

Keshav Singh
Keshav Singh
Numerade Educator
09:35

Problem 18

At an intersection of hospital hallways, a convex spherical mirror is mounted high on a wall to help people avoid collisions. The magnitude of the mirror's radius of curvature is $0.550 \mathrm{m}$. (a) Locate the image of a patient $10.0 \mathrm{m}$ from the mirror. (b) Indicate whether the image is upright or inverted. (c) Determine the magnification of the image.

Matthew Kegley
Matthew Kegley
Numerade Educator
03:37

Problem 19

A spherical mirror is to be used to form an image 5.00 times the size of an object on a screen located $5.00 \mathrm{m}$ from the object. (a) Is the mirror required concave or convex? (b) What is the required radius of curvature of the mirror? (c) Where should the mirror be positioned relative to the object?

Keshav Singh
Keshav Singh
Numerade Educator
07:14

Problem 20

A certain Christmas tree ornament is a silver sphere having a diameter of $8.50 \mathrm{cm} .$ (a) If the size of an image created by reflection in the ornament is three-fourths the reflected object's actual size, determine the object's location. (b) Use a principal-ray diagram to determine whether the image is upright or inverted.

Vishal Gupta
Vishal Gupta
Numerade Educator
05:13

Problem 21

A Dedicated sports car enthusiast polishes the inside and outside surfaces of a hubcap that is a thin section of a sphere. When she looks into one side of the hubcap, she sees an image of her face $30.0 \mathrm{cm}$ in back of the hubcap. She then flips the hubcap over and sees another image of her face $10.0 \mathrm{cm}$ in back of the hubcap. (a) How far is her face from the hubcap?
(b) What is the radius of curvature of the hubcap?

Vishal Gupta
Vishal Gupta
Numerade Educator
01:31

Problem 22

You unconsciously estimate the distance to an object from the angle it subtends in your field of view. This angle $\theta$ in radians is related to the linear height of the object $h$ and to the distance $d$ by $\theta=h / d$. Assume you are driving a car and another car, $1.50 \mathrm{m}$ high, is $24.0 \mathrm{m}$ behind you. (a) Suppose your car has a flat passenger-side rear-view mirror, $1.55 \mathrm{m}$ from your eyes. How far from your eyes is the image of the car following you? (b) What angle does the image subtend in your field of view? (c) What If? Now suppose your car has a convex rear-view mirror with a radius of curvature of magnitude $2.00 \mathrm{m}$ (as suggested in Fig. 26.14 ). How far from your eyes is the image of the car behind you? (d) What angle does the image subtend at your eyes? (e) Based on its angular size, how far away does the following car appear to be?

Dominador Tan
Dominador Tan
Numerade Educator
03:21

Problem 23

One end of a long glass rod $(n=1.50)$ is formed into a convex surface with a radius of curvature of magnitude $6.00 \mathrm{cm}$ An object is located in air along the axis of the rod. Find the image positions corresponding to object distances of (a) $20.0 \mathrm{cm},$ (b) $10.0 \mathrm{cm},$ and (c) $3.00 \mathrm{cm}$ from the convex end of the rod.

Keshav Singh
Keshav Singh
Numerade Educator
01:21

Problem 24

A cubical block of ice $50.0 \mathrm{cm}$ on a side is placed over a speck of dust on a level floor. Find the location of the image of the speck as viewed from above. The index of refraction of ice is 1.309.

Keshav Singh
Keshav Singh
Numerade Educator
25:34

Problem 25

A flint glass plate rests on the bottom of an aquarium tank. The plate is $8.00 \mathrm{cm}$ thick (vertical dimension) and is covered with a layer of water $12.0 \mathrm{cm}$ deep. Calculate the apparent thickness of the plate as viewed from straight above the water.

Matthew Kegley
Matthew Kegley
Numerade Educator
02:01

Problem 26

A simple model of the human eye ignores its lens entirely. Most of what the eye does to light happens at the outer surface of the transparent cornea. Assume that this surface has a radius of curvature of $6.00 \mathrm{mm}$ and that the eyeball contains just one fluid with a refractive index of $1.40 .$ Prove that a very distant object will be imaged on the retina, $21.0 \mathrm{mm}$ behind the cornea. Describe the image.

Keshav Singh
Keshav Singh
Numerade Educator
01:13

Problem 27

A glass sphere $(n=1.50)$ with a radius of $15.0 \mathrm{cm}$ has a tiny air bubble $5.00 \mathrm{cm}$ above its center. The sphere is viewed looking down along the extended radius containing the bubble. What is the apparent depth of the bubble below the surface of the sphere?

Salamat Ali
Salamat Ali
Numerade Educator
03:52

Problem 28

A goldfish is swimming at $2.00 \mathrm{cm} / \mathrm{s}$ toward the front wall of a rectangular aquarium. What is the apparent speed of the fish measured by an observer looking in from outside the front wall of the tank?

Vishal Gupta
Vishal Gupta
Numerade Educator
01:26

Problem 29

A contact lens is made of plastic with an index of refraction of $1.50 .$ The lens has an outer radius of curvature of $+2.00 \mathrm{cm}$ and an inner radius of curvature of $+2.50 \mathrm{cm}$ What is the focal length of the lens?

Keshav Singh
Keshav Singh
Numerade Educator
05:26

Problem 30

An object is located $20.0 \mathrm{cm}$ to the left of a diverging lens having a focal length $f=-32.0 \mathrm{cm} .$ Determine (a) the location and (b) the magnification of the image. (c) Construct a ray diagram for this arrangement.

Vishal Gupta
Vishal Gupta
Numerade Educator
02:45

Problem 31

A thin lens has a focal length of $25.0 \mathrm{cm} .$ Locate and describe the image when the object is placed (a) $26.0 \mathrm{cm}$ and
(b) $24.0 \mathrm{cm}$ in front of the lens.

Keshav Singh
Keshav Singh
Numerade Educator
01:16

Problem 32

A converging lens has a focal length of $20.0 \mathrm{cm}$. Locate the image for object distances of (a) $40.0 \mathrm{cm},$ (b) $20.0 \mathrm{cm},$ and (c) $10.0 \mathrm{cm} .$ For each case, state whether the image is real or virtual and upright or inverted. Find the magnification in each case.

Mayukh Banik
Mayukh Banik
Numerade Educator
04:38

Problem 33

The left face of a biconvex lens has a radius of curvature of magnitude $12.0 \mathrm{cm},$ and the right face has a radius of curvature of magnitude $18.0 \mathrm{cm} .$ The index of refraction of the glass is 1.44 . (a) Calculate the focal length of the lens for light incident from the left. (b) What If? After the lens is turned around to interchange the radii of curvature of the two faces, calculate the focal length of the lens for light incident from the left.

Vishal Gupta
Vishal Gupta
Numerade Educator
02:25

Problem 34

Suppose an object has thickness $d p$ so that it extends from object distance $p$ to $p+d p .$ (a) Prove that the thickness $d q$ of its image is given by $\left(-q^{2} / p^{2}\right) d p .$ (b) The longitudinal magnification of the object is $M_{\text {long }}=d q / d p .$ How is the longitudinal magnification related to the lateral magnification $M ?$

Keshav Singh
Keshav Singh
Numerade Educator
01:41

Problem 35

The projection lens in a certain slide projector is a single thin lens. A slide $24.0 \mathrm{mm}$ high is to be projected so that its image fills a screen $1.80 \mathrm{m}$ high. The slide-to-screen distance is $3.00 \mathrm{m} .$ (a) Determine the focal length of the projection lens.
(b) How far from the slide should the lens of the projector be placed so as to form the image on the screen?

Mayukh Banik
Mayukh Banik
Numerade Educator
03:46

Problem 36

The use of a lens in a certain situation is described by the equation $$\frac{1}{p}+\frac{1}{-3.50 p}=\frac{1}{7.50 \mathrm{cm}}$$ Determine (a) the object distance and (b) the image distance.
(c) Use a ray diagram to obtain a description of the image.
(d) Identify a practical device described by the given equation and write the statement
of a problem for which the equation appears in the solution.

Ajay Singhal
Ajay Singhal
Numerade Educator
01:54

Problem 37

The nickel's image in Figure $P 26.37$ has twice the diameter of the nickel and is $2.84 \mathrm{cm}$
from the lens. Determine the focal length of the lens.

Keshav Singh
Keshav Singh
Numerade Educator
02:21

Problem 38

In Figure $\mathrm{P} 26.38,$ a thin converging lens of focal length $14.0 \mathrm{cm}$ forms an image of the square abcd, which is $h_{c}=h_{b}=10.0 \mathrm{cm}$ high and lies between distances of $p_{d}=20.0 \mathrm{cm}$ and $p_{a}=30.0 \mathrm{cm}$ from the lens. Let $a^{\prime}, b^{\prime}, c^{\prime},$ and $d^{\prime}$ represent the respective corners of the image. Let $q_{a}$ represent the image distance for points $a^{\prime}$ and $b^{\prime}, q_{d}$ represent the image distance for points $c^{\prime}$ and $d^{\prime}, h_{b}^{\prime}$ represent the distance from point $b^{\prime}$ to the axis, and $h_{c}^{\prime}$ represent the height of $c^{\prime} \cdot(\mathrm{a})$ Find $q_{a}, q_{d}, h_{b}^{\prime},$ and $h_{c}^{\prime} .$ (b) Make a sketch of the image. (c) The area of the object is $100 \mathrm{cm}^{2}$. By carrying out the following steps, you will evaluate the area of the image. Let $q$ represent the image distance of any point between $a^{\prime}$ and $d^{\prime},$ for which the object distance is $p .$ Let $h^{\prime}$ represent the distance from the axis to the point at the edge of the image between $b^{\prime}$ and $c^{\prime}$ at image distance $q$. Demonstrate that $$\left|h^{\prime}\right|=10.0 q\left(\frac{1}{14.0}-\frac{1}{q}\right)$$ where $h^{\prime}$ and $q$ are in centimeters. (d) Explain why the geometric area of the image is given by $$\int_{q_{a}}^{q_{a}}\left|h^{\prime}\right| d q$$ (e) Carry out the integration to find the area of the image.

Dominador Tan
Dominador Tan
Numerade Educator
02:47

Problem 39

Figure $\mathrm{P} 26.39$ diagrams a cross-section of a camera. It has a single lens of focal length $65.0 \mathrm{mm}$ which is to form an image on the CCD (charge-coupled device) at the back of the cam-
era. Suppose the position of the lens has been adjusted to focus the image of a distant object. How far and in what direction must the lens be moved to form a sharp image of an object that is $2.00 \mathrm{m}$ away?

Keshav Singh
Keshav Singh
Numerade Educator
05:06

Problem 40

Why is the following situation impossible? An illuminated object is placed a distance $d=2.00 \mathrm{m}$ from a screen. By placing a converging lens of focal length $f=60.0 \mathrm{cm}$ at two locations between the object and the screen, a sharp, real image of the object can be formed on the screen. In one location of the lens, the image is larger than the object, and in the other, the image is smaller.

Vishal Gupta
Vishal Gupta
Numerade Educator
04:00

Problem 41

An antelope is at a distance of $20.0 \mathrm{m}$ from a converging lens of focal length $30.0 \mathrm{cm} .$ The lens forms an image of the animal. (a) If the antelope runs away from the lens at a speed of $5.00 \mathrm{m} / \mathrm{s},$ how fast does the image move? (b) Does the image move toward or away from the lens?

Keshav Singh
Keshav Singh
Numerade Educator
02:20

Problem 42

An object is at a distance $d$ to the left of a flat screen. A converging lens with focal length $f<d / 4$ is placed between object and screen. (a) Show that two lens positions exist that form an image on the screen and determine how far these positions are from the object. (b) How do the two images differ from each other?

Mayukh Banik
Mayukh Banik
Numerade Educator
01:45

Problem 43

An object located $32.0 \mathrm{cm}$ in front of a lens forms an image on a screen $8.00 \mathrm{cm}$ behind the lens. (a) Find the focal length of the lens. (b) Determine the magnification. (c) Is the lens converging or diverging?

Keshav Singh
Keshav Singh
Numerade Educator
01:35

Problem 44

A nearsighted person cannot see objects clearly beyond $25.0 \mathrm{cm}$ (her far point). If she has no astigmatism and contact lenses are prescribed for her, what (a) power and (b) type of lens are required to correct her vision?

Keshav Singh
Keshav Singh
Numerade Educator
02:04

Problem 45

The near point of a person's eye is $60.0 \mathrm{cm} .$ To see objects clearly at a distance of $25.0 \mathrm{cm},$ what should be the (a) focal length and (b) power of the appropriate corrective lens? (Neglect the distance from the lens to the eye.)

Keshav Singh
Keshav Singh
Numerade Educator
08:55

Problem 46

A patient has a near point of $45.0 \mathrm{cm}$ and far point of $85.0 \mathrm{cm} .$ (a) Can a single lens correct the patient's vision? Explain the patient's options. (b) Calculate the power lens needed to correct the near point so that the patient can see objects $25.0 \mathrm{cm}$ away. Neglect the eye-lens distance. (c) Calculate the power lens needed to correct the patient's far point, again neglecting the eye-lens distance.

Vishal Gupta
Vishal Gupta
Numerade Educator
01:58

Problem 47

The accommodation limits for a nearsighted person's eyes are $18.0 \mathrm{cm}$ and $80.0 \mathrm{cm} .$ When he wears his glasses, he can see faraway objects clearly. At what minimum distance is he able to see objects clearly?

Keshav Singh
Keshav Singh
Numerade Educator
02:14

Problem 48

A person sees clearly wearing eyeglasses that have a power of -4.00 diopters when the lenses are $2.00 \mathrm{cm}$ in front of the eyes. (a) What is the focal length of the lens?
(b) Is the person nearsighted or farsighted? (c) If the person wants to switch to contact lenses placed directly on the eyes, what lens power should be prescribed?

Keshav Singh
Keshav Singh
Numerade Educator
03:03

Problem 49

A person is to be fitted with bifocals. She can see clearly when the object is between $30 \mathrm{cm}$ and $1.5 \mathrm{m}$ from the eye. (a) The upper portions of the bifocals (Fig. $P 26.49$ ) should be designed to enable her to see distant objects clearly. What power should they have? (b) The lower portions of the bifocals should enable her to see objects located $25 \mathrm{cm}$ in front of the eye. What power should they have?

Netra Sharma
Netra Sharma
University of Wisconsin - Milwaukee
05:05

Problem 50

A certain child's near point is $10.0 \mathrm{cm} ;$ her far point (with eyes relaxed) is $125 \mathrm{cm}$. Each eye lens is $2.00 \mathrm{cm}$ from the retina. (a) Between what limits, measured in diopters, does the power of this lens-cornea combination vary? (b) Calculate the power of the eyeglass lens the child should use for relaxed distance vision. Is the lens converging or diverging?

Eduard Sanchez
Eduard Sanchez
Numerade Educator
02:21

Problem 51

You are designing an endoscope for use inside an air-filled body cavity. A lens at the end of the endoscope will form an image covering the end of a bundle of optical fibers. This image will then be carried by the optical fibers to an eyepiece lens at the outside end of the fiber-scope. The radius of the bundle is $1.00 \mathrm{mm}$. The scene within the body that is to appear within the image fills a circle of radius $6.00 \mathrm{cm} .$ The lens will be located $5.00 \mathrm{cm}$ from the tissues you wish to observe. (a) How far should the lens be located from the end of an optical fiber bundle? (b) What is the focal length of the lens required?

Keshav Singh
Keshav Singh
Numerade Educator
02:59

Problem 52

Consider the endoscope probe used for treating hydrocephalus and shown in Figure 26.34 . The spherical end, with refractive index 1.50 , is attached to an optical fiber bundle of radius $1.00 \mathrm{mm}$, which is smaller than the radius of the sphere. The center of the spherical end is on the central axis of the bundle. Consider laser light that travels precisely parallel to the central axis of the bundle and then refracts out from the surface of the sphere into air. (a) In Figure 26.34 , does light that refracts out of the sphere and travels toward the upper right come from the top half of the sphere or from the bottom half of the sphere? (b) If laser light that travels along the edge of the optical fiber bundle refracts out of the sphere tangent to the surface of the sphere, what is the radius of the sphere? (c) Find the angle of deviation of the ray considered in part (b), that is, the angle by which its direction changes as it leaves the sphere. (d) Show that the ray considered in part (b) has a greater angle of deviation than any other ray. Show that the light from all parts of the optical fiber bundle does not refract out of the sphere with spherical symmetry, but rather fills a cone around the forward direction. Find the angular diameter of the cone. (e) In reality, however, laser light can diverge from the sphere with approximate spherical symmetry. What considerations that we have not addressed will lead to this approximate spherical symmetry in practice?

Dominador Tan
Dominador Tan
Numerade Educator
08:01

Problem 53

The object in Figure $\mathrm{P} 26.53$ is midway between the lens and the mirror, which are separated by a distance $d=$ $25.0 \mathrm{cm} .$ The magnitude of the mirror's radius of curvature is $20.0 \mathrm{cm}$ and the lens has a focal length of $-16.7 \mathrm{cm} .$ (a) Considering only the light that leaves the object and travels first toward the mirror, locate the final image formed by this system. (b) Is this image real or virtual? (c) Is it upright or inverted? (d) What is the overall magnification?

Vishal Gupta
Vishal Gupta
Numerade Educator
08:38

Problem 54

In a darkened room, a burning candle is placed 1.50 $\mathrm{m}$ from a white wall. A lens is placed between the candle and the wall at a location that causes a larger, inverted image to form on the wall. When the lens is in this position, the object distance is $p_{1} .$ When the lens is moved $90.0 \mathrm{cm}$ toward the wall, another image of the candle is formed on the wall. From this information, we wish to find $p_{1}$ and the focal length of the lens. (a) From the lens equation for the first position of the lens, write an equation relating the focal length $f$ of the lens to the object distance $p_{1},$ with no other variables in the equation. (b) From the lens equation for the second position of the lens, write another equation relating the focal length $f$ of the lens to the object distance $p_{1}$
(c) Solve the equations in parts (a) and (b) simultaneously to find $p_{1}$. (d) Use the value in part (c) to find the focal length $f$ of the lens.

Vishal Gupta
Vishal Gupta
Numerade Educator
02:50

Problem 55

The distance between an object and its upright image is $20.0 \mathrm{cm} .$ If the magnification is 0.500 , what is the focal length of the lens being used to form the image?

Mayukh Banik
Mayukh Banik
Numerade Educator
04:28

Problem 56

The distance between an object and its upright image is $d .$ If the magnification is $M,$ what is the focal length of the lens being used to form the image?

Vishal Gupta
Vishal Gupta
Numerade Educator
02:42

Problem 57

The lens and mirror in Figure $\mathrm{P} 26.57$ are separated by $d=1.00 \mathrm{m}$ and have focal lengths of $+80.0 \mathrm{cm}$ and $-50.0 \mathrm{cm},$ respectively. An object is placed $p=1.00 \mathrm{m}$ to the left of the lens as shown. (a) Locate the final image, formed by light that has gone through the lens twice. (b) Determine the overall magnification of the image and (c) state whether the image is upright or inverted.

Narayan Hari
Narayan Hari
Numerade Educator
07:42

Problem 58

Why is the following situation impossible? Consider the lens-mirror combination shown in Figure $\mathrm{P} 26.58$ The lens has a focal length of $f_{\mathrm{L}}=$ $0.200 \mathrm{m},$ and the mirror has a focal length of $f_{\mathrm{M}}=0.500 \mathrm{m} .$ The lens and mirror are placed a distance $d=1.30 \mathrm{m}$ apart, and an object is placed at $p=0.300 \mathrm{m}$ from the lens. By moving a screen to various positions to the left of the lens, a student finds two different positions of the screen that produce a sharp image of the object. One of these positions corresponds to light leaving the object and traveling to the left through the lens. The other position corresponds to light traveling to the right from the object, reflecting from the mirror and then passing through the lens.

Vishal Gupta
Vishal Gupta
Numerade Educator
01:55

Problem 59

A spherical lightbulb of diameter $3.20 \mathrm{cm}$ radiates light equally in all directions, with power $4.50 \mathrm{W.}$ (a) Find the light intensity at the surface of the lightbulb. (b) Find the light intensity $7.20 \mathrm{m}$ away from the center of the lightbulb. (c) At this 7.20 -m distance, a lens is set up with its axis pointing toward the lightbulb. The lens has a circular face with a diameter of $15.0 \mathrm{cm}$ and has a focal length of $35.0 \mathrm{cm}$ Find the diameter of the light-bulb's image. (d) Find the light intensity at the image.

Dominador Tan
Dominador Tan
Numerade Educator
02:14

Problem 60

Derive the lens-makers' equation as follows. Consider an object in vacuum at $p_{1}=\infty$ from a first refracting surface of radius of curvature $R_{1}$. Locate its image. Use this image as the object for the second refracting surface, which has nearly the same location as the first because the lens is thin Locate the final image, proving it is at the image distance $q_{2}$ given by $$\frac{1}{q_{2}}=(n-1)\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right)$$

Keshav Singh
Keshav Singh
Numerade Educator
04:24

Problem 61

An object is placed $12.0 \mathrm{cm}$ to the left of a diverging lens of focal length $-6.00 \mathrm{cm} .$ A converging lens of focal length $12.0 \mathrm{cm}$ is placed a distance $d$ to the right of the diverging lens. Find the distance $d$ so that the final image is infinitely far away to the right.

Vishal Gupta
Vishal Gupta
Numerade Educator
04:57

Problem 62

An object is placed a distance $p$ to the left of a diverging lens of focal length $f_{1}$. A converging lens of focal length $f_{2}$ is placed a distance $d$ to the right of the diverging lens. Find the distance $d$ so that the final image is infinitely far away to the right.

Vishal Gupta
Vishal Gupta
Numerade Educator
01:41

Problem 63

The lens-makers' equation applies to a lens immersed in a liquid if $n$ in the equation is replaced by $n_{2} / n_{1} .$ Here $n_{2}$ refers to the index of refraction of the lens material and $n_{1}$ is that of the medium surrounding the lens. (a) $A$ certain lens has focal length $79.0 \mathrm{cm}$ in air and index of refraction $1.55 .$ Find its focal length in water. (b) A certain mirror has focal length $79.0 \mathrm{cm}$ in air. Find its focal length in water.

Mayukh Banik
Mayukh Banik
Numerade Educator
02:14

Problem 64

In many applications, it is necessary to expand or decrease the diameter of a beam of parallel rays of light, which can be accomplished by using a converging lens and a diverging lens in combination. Suppose you have a converging lens of focal length $21.0 \mathrm{cm}$ and a diverging lens of focal length $-12.0 \mathrm{cm} .$ (a) How can you arrange these lenses to increase the diameter of a beam of parallel rays? (b) By what factor will the diameter increase?

James Kiss
James Kiss
Numerade Educator
01:31

Problem 65

A real object is located at the zero end of a meter-stick. A large concave spherical mirror at the 100 -cm end of the meter-stick forms an image of the object at the 70.0 -cm position. A small convex spherical mirror placed at the $20.0-\mathrm{cm}$ position forms a final image at the 10.0 -cm point. What is the radius of curvature of the convex mirror?

Keshav Singh
Keshav Singh
Numerade Educator
04:06

Problem 66

A $z$ oom lens system is a combination of lenses that produces a variable magnification of a fixed object as it maintains a fixed image position. The magnification is varied by moving one or more lenses along the axis. Multiple lenses are used in practice, but the effect of zooming in on an object can be demonstrated with a simple two-lens system. An object, two converging lenses, and a screen are mounted on an optical bench. Lens 1 , which is to the right of the object, has a focal length of $f_{1}=5.00 \mathrm{cm},$ and lens $2,$ which is to the right of the first lens, has a focal length of $f_{2}=10.0 \mathrm{cm} .$ The screen is to the right of lens $2 .$ Initially, an object is situated at a distance of $7.50 \mathrm{cm}$ to the left of lens $1,$ and the image formed on the screen has a magnification of $+1.00 .$ (a) Find the distance between the object and the screen. (b) Both lenses are now moved along their common axis while the object and the screen maintain fixed positions until the image formed on the screen has a magnification of $+3.00 .$ Find the displacement of each lens from its initial position in part (a). (c) Can the lenses be displaced in more than one way?

Dominador Tan
Dominador Tan
Numerade Educator
01:12

Problem 67

The disk of the Sun subtends an angle of $0.533^{\circ}$ at the Earth. What are (a) the position and (b) the diameter of the solar image formed by a concave spherical mirror with a radius of curvature of magnitude $3.00 \mathrm{m} ?$

Dominador Tan
Dominador Tan
Numerade Educator
01:28

Problem 68

A floating strawberry illusion is achieved with two parabolic mirrors, each having a focal length $7.50 \mathrm{cm},$ facing each other as shown in Figure $\mathrm{P} 26.68 .$ If a strawberry is placed on the lower mirror, an image of the strawberry is formed at the small opening at the center of the top mirror, $7.50 \mathrm{cm}$ above the lowest point of the bottom mirror. The position of the eye in Figure $\mathrm{P} 26.68$ corresponds to the view of the apparatus in Figure $\mathrm{P} 26.68 \mathrm{b}$. Consider the light path marked $A$. Notice that this light path is blocked by the upper mirror so that the strawberry itself is not directly observable. The light path marked $B$ corresponds to the eye viewing the image of the strawberry that is formed at the opening at the top of the apparatus. (a) Show that the final image is formed at that location and describe its characteristics. (b) A very startling effect is to shine a flashlight beam on this image. Even at a glancing angle, the incoming light beam is seemingly reflected from the image! Explain.

Dominador Tan
Dominador Tan
Numerade Educator
01:46

Problem 69

A parallel beam of light enters a glass hemisphere perpendicular to the flat face as shown in Figure $\mathrm{P} 26.69 .$ The magnitude of the radius of the hemisphere is $R=6.00 \mathrm{cm},$ and its index of refraction is $n=1.560 .$ Assuming paraxial rays, determine the point at which the beam is focused.

Keshav Singh
Keshav Singh
Numerade Educator
10:44

Problem 70

An object $2.00 \mathrm{cm}$ high is placed $40.0 \mathrm{cm}$ to the left of a converging lens having a focal length of $30.0 \mathrm{cm} .$ A diverging lens with a focal length of $-20.0 \mathrm{cm}$ is placed $110 \mathrm{cm}$ to the right of the converging lens. Determine (a) the position and (b) the magnification of the final image. (c) Is the image upright or inverted? (d) What If? Repeat parts
(a) through (c) for the case in which the second lens is a converging lens having a focal length of $20.0 \mathrm{cm}$.

Vishal Gupta
Vishal Gupta
Numerade Educator
07:08

Problem 71

An observer to the right of the mirror-lens combination shown in Figure $\mathrm{P} 26.71$ (not to scale) sees two real images that are the same size and in the same location. One image is upright, and the other is inverted. Both images are 1.50 times larger than the object. The lens has a focal length of $10.0 \mathrm{cm} .$ The lens and mirror are separated by $40.0 \mathrm{cm} .$ Determine the focal length of the mirror.

Vishal Gupta
Vishal Gupta
Numerade Educator
09:59

Problem 72

Figure $\mathrm{P} 26.72$ shows a thin converging lens for which the radii of curvature of its surfaces have magnitudes of $9.00 \mathrm{cm}$ and $11.0 \mathrm{cm} .$ The lens is in front of a concave spherical mirror with the radius of curvature $R=8.00 \mathrm{cm} .$ Assume the focal points $F_{1}$ and $F_{2}$ of the lens are $5.00 \mathrm{cm}$ from the center of the lens. (a) Determine the index of refraction of the lens material. The lens and mirror are $20.0 \mathrm{cm}$ apart, and an object is placed $8.00 \mathrm{cm}$ to the left of the lens. Determine
(b) the position of the final image and (c) its magnification as seen by the eye in the figure. (d) Is the final image inverted or upright? Explain.

Vishal Gupta
Vishal Gupta
Numerade Educator
04:06

Problem 73

Assume the intensity of sunlight is $1.00 \mathrm{kW} / \mathrm{m}^{2}$ at a particular location. A highly reflecting concave mirror is to be pointed toward the Sun to produce a power of at least $350 \mathrm{W}$ at the image point. (a) Assuming the disk of the Sun subtends an angle of $0.533^{\circ}$ at the Earth, find the required radius $R_{a}$ of the circular face area of the mirror. (b) Now suppose the light intensity is to be at least $120 \mathrm{kW} / \mathrm{m}^{2}$ at the image. Find the required relationship between $R_{a}$ and the radius of curvature $R$ of the mirror.

Dominador Tan
Dominador Tan
Numerade Educator