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Fundamentals of Optics

Francis Jenkins, Harvey White

Chapter 4

Thin Lenses - all with Video Answers

Educators

Chapter Questions

02:46

Problem 1

An object located $12.0 \mathrm{~cm}$ in front of a thin lens has its image formed on the opposite side $42.0 \mathrm{~cm}$ from the lens. Calculate ( $a$ ) the focal length of the lens and (b) the lens power.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
05:27

Problem 2

An object $2.50 \mathrm{~cm}$ high is placed $12.0 \mathrm{~cm}$ in front of a thin lens of focal length $3.0 \mathrm{~cm}$. Calculate ( $a$ ) the image distance, $(b)$ the magnification, and $(c)$ the nature of the image.
(d) Check your answers by a graph.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
03:11

Problem 3

The two faces of a thin lens have radii $r_{1}=+10.0 \mathrm{~cm}$ and $r_{2}=-25.0 \mathrm{~cm}$, respectively. The lens is made of glass of index $1.740 .$ Calculate $(a)$ the focal length and $(b)$ the power of the lens.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
02:42

Problem 4

The two faces of a thin lens have radii $r_{1}=+10.0 \mathrm{~cm}$ and $r_{2}=-25.0 \mathrm{~cm}$, respectively. The lens is made of glass of index $1.740 .$ Calculate $(a)$ the focal length and $(b)$ the power of the lens.

Himanshu Gusai
Himanshu Gusai
Numerade Educator
02:42

Problem 5

An equiconcave lens is to be made of flint glass of index $1.750 .$ Calculate the radii of curvature if it is to have a power of $-3.0 \mathrm{D}$.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
02:18

Problem 6

A plano-convex lens is to be made of light flint glass of index 1.680. Caiculate the radius of curvature necessary to give the lens a power of $4.5 \mathrm{D}$.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
06:09

Problem 7

Two lenses with focal lengths $f_{1}=+5.0 \mathrm{~cm}$ and $f_{2}=+10.0 \mathrm{~cm}$ are located $5.0 \mathrm{~cm}$ apart. If an object $2.50 \mathrm{~cm}$ high is located $15.0 \mathrm{~cm}$ in front of the first lens, find $(a)$ the position and $(b)$ the size of the final image.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
05:16

Problem 8

A converging lens is used to focus a sharp image of a candle flame on a screen. Without moving the candle flame a second lens with radii $r_{1}=+10.0 \mathrm{~cm}$ and $r_{2}=-20.0 \mathrm{~cm}$ and index $1.650$ is placed in the converging beam $30.0 \mathrm{~cm}$ from the screen. $(a)$ Calculate the power of the second lens. (b) How close to the second lens should the screen now be placed to obtain a sharp image of the flame? (c) Make a graph of this experiment.

Saikat Chatterjee
Saikat Chatterjee
Numerade Educator
04:18

Problem 9

A double-convex lens is to be made of glass having a refractive index of $1.580 .$ If one surface is to have twice the radius of the other and the focal length is to be $+6.0 \mathrm{~cm}$, find the radii.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
07:16

Problem 10

Two lenses having focal lengths $f_{1}=+9.0 \mathrm{~cm}$ and $f_{2}=-18.0 \mathrm{~cm}$ are placed $3.0 \mathrm{~cm}$ apart. If an object $2.50 \mathrm{~cm}$ high is located $20.0 \mathrm{~cm}$ in front of the first lens, calculate
(a) the position and $(b)$ the size of the final image. (c) Check your answer graphically.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
03:28

Problem 11

A lantern slide $8.0 \mathrm{~cm}$ high is located $3.50 \mathrm{~m}$ from a projection screen. What is the focal length of the lens that will be required to project an image $1.0 \mathrm{~m}$ high?

Rajesh Kumar
Rajesh Kumar
Numerade Educator
03:30

Problem 12

An object is located $1.60 \mathrm{~m}$ from a white screen. A lens of what focal length will be required to form a real and inverted image on the screen with a magnification of $-6.0$ ?

Rajesh Kumar
Rajesh Kumar
Numerade Educator
04:24

Problem 13

Three thin lenses have powers $+1.50,-2.80$, and $3.40 \mathrm{D}$, respectively. What are all the possible powers that can be obtained with these three lenses using one, two, or three at a time in contact?

Rajesh Kumar
Rajesh Kumar
Numerade Educator
07:03

Problem 14

Two thin lenses having the following radii of curvature and index are placed in contact. For the first lens $r_{1}=+12.0 \mathrm{~cm}, r_{2}=-18.0 \mathrm{~cm}$, and $n=1.560$, and for the second lens $r_{1}=-30.0 \mathrm{~cm}, r_{2}=+20.0 \mathrm{~cm}$, and $n=1.650 .$ Find their (a) individual powers, (b) combined power, (c) individual focal lengths, and $(d)$ combined focal length.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
06:16

Problem 15

An object $2.50 \mathrm{~cm}$ high is located $15.0 \mathrm{~cm}$ in front of a lens of $+5.0 \mathrm{~cm}$ focal length. A lens with a focal length of $-12.0 \mathrm{~cm}$ is placed $2.50 \mathrm{~cm}$ beyond this converging lens. Find $(a)$ the position and $(b)$ the size of the final image.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
07:17

Problem 16

An object $2.50 \mathrm{~cm}$ high is located $8.0 \mathrm{~cm}$ in front of a lens of $-2.40 \mathrm{~cm}$ focal length. A lens of $+5.0 \mathrm{~cm}$ focal length is placed $1.50 \mathrm{~cm}$ behind the first lens. Find $(a)$ the position and $(b)$ the size of the final image. (c) Draw a graph.

Rajesh Kumar
Rajesh Kumar
Numerade Educator
05:12

Problem 17

Three lenses with focal lengths of $+8.40,-4,60$, and $+6.20 \mathrm{~cm}$, respectively, are located one behind each other in this order and $2.0 \mathrm{~cm}$ apart. $(a)$ If parallel light is incident on the first lens, how far behind the third lens will the light be brought to a focus?
(b) Draw a scale diagram.

Rajesh Kumar
Rajesh Kumar
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06:45

Problem 18

An object $3.50 \mathrm{~cm}$ high is located $8.0 \mathrm{~cm}$ in front of a lens of $-7.0 \mathrm{~cm}$ focal length. A lens of $+4.50 \mathrm{~cm}$ focal length is placed $3.5 \mathrm{~cm}$ behind the first lens. Find $(a)$ the position and (b) the size of the image. (c) Make a diagram to scale.

Rajesh Kumar
Rajesh Kumar
Numerade Educator