CONVEX LENSES 18 1 Lenses n A convex
- Slides: 117
CONVEX LENSES
18. 1 Lenses n A convex lens (or a converging lens) converges parallel light rays passing through it. Various shapes of convex lenses
Terms for describing lenses n Optical centre is the centre of a lens.
n Principal axis is the line passing through the optical centre and perpendicular to the lens.
n For a convex lens, the principal focus is the point to which the parallel rays converge after passing through the lens.
n Focal length is the distance between the principal focus and the optical centre.
n Focal plane is the plane passing through the focus and normal to the principal axis. focal planes
18. 2 Properties of images formed by lenses Construction rules for drawing ray diagrams n For convex lenses Rule 1: The direction of the light ray passing through the optical centre of a convex lens remains unchanged.
Rule 2: The light ray parallel to the principal axis will pass through the principal focus F after refracted by the convex lens.
Rule 3: The light ray passing through the principal focus F¢ becomes parallel to the principal axis after refracted by the convex lens.
1. In each of the following cases, a ray is incident on a convex lens. Draw the refracted ray. (a)
n Symbols for a convex lens
Drawing ray diagram to locate the image. 1. Draw 2 light rays from the tip of the object to the lens and draw their corresponding refracted rays. 2. Extend the refracted rays. The intersection point is the position of the image.
image
n 1. Object within F¢: n The image is formed on the same side of the lens. n Nature of the image: erect, magnified, virtual Image formed by convex lens
n 2. Object at F¢: n The image is formed at infinity.
n 3. Object between F¢ and 2 F¢: n The image is formed on the other side of the lens beyond 2 F. n Nature of the image: inverted, magnified, real
n 4. Object at 2 F¢: n The image is formed on the other side of the lens at 2 F. n Nature of the image: inverted, same size as the object, real
n 5. Object beyond 2 F¢: n The image is formed on the other side of the lens between F and 2 F. n Nature of the image: inverted, diminished, real
Nature of images formed by convex lenses n 6. Distant object: n The image is formed on the focal plane on the other side of the lens. n Nature of the image: inverted, diminished, real
Do experiment 18. 2 (book P. 174)
Linear magnification of images Linear magnification n Dimensionless (No unit) n Definition: linear magnification m = height of the image height of the object
• Also, ABC ~ A’B’C’ linear magnificat ion m = image distance v object distance u
linear magnification m = height of the image height of the object If the image is magnified, m _____1. > If the image is same size as object, m __ 1 = If the image is diminished, m _____ 1 <
Notes Worked examples - 1
15 the size of the image = _____ cm the image distance = 30 cm The image is erect, virtual, magnified
Worked examples - 1 Draw the refracted rays for p, q and r. p r q All the refracted rays will pass through / seem to come from image.
2. Locate the image first by drawing two typical rays. All the refracted rays will pass through / seem to come from image.
3. An object of height 10 cm is placed 30 cm in front of a convex lens. The focal length of the lens is 15 cm. Draw a ray diagram to find the linear magnification of the image. Rough work: f = 15 cm, u = 30 cm, u = 2 f Image is formed at 2 F, real, inverted and same size.
3. F F
3. Image distance = 30 cm magnification = 10 cm / 10 cm = 1
4. An object of height 20 cm is placed 30 cm in front of a convex lens of focal length 20 cm. (a) Show graphically the formation of the image by using a suitable scale. Rough work: f = 20 cm, u = 30 cm, f < u < 2 f Image is formed behind 2 f, real, inverted and magnified.
Lens, object, F scale 2 typical rays image 20 cm 10 cm O I F F
(b) What are the properties of the image? Real, inverted, magnified. (c ) Find the magnification. m = 40 / 20 = 2
5. An object of height 10 cm is placed 10 cm in front of a convex lens of focal length 15 cm. (a) Show graphically the formation of the image by using a suitable scale. f = 15 cm, u = 10 cm, u < f Image is virtual, erect, magnified.
5 cm 10 cm I F F
(b) What are the properties of the image? The image is virtual, erect and magnified. (c ) Find the magnification. m = 30/10 = 3
6. Draw the refracted rays of p, q, r and s. I
7. (a) I (b) m = 5 /2. 5= 2
8 (a) real (b) On the other side of the lens. I O Object is 90 cm from the lens.
9. (a) A convex lens is placed 10 cm in front of an object of height 2 cm. AP is the principal axis of the lens. If an image of height 6 cm is formed on a screen, (i) find the magnification of the image, Magnification = (ii) Real and inverted
9 (a) (iii) I F (iv) The image distance is 30 cm on the other side of the lens. The focal length of the lens is 7. 5 cm.
New image F F (b) Move the screen towards the lens. I
(c ) When the lens was close to the object, virtual image is formed. Virtual image can only be seen by eyes and cannot be formed on screen.
10. A lens is held close over a graph paper. magnified (a) Convex lens (b) Virtual, erect (c) m = 2
F (d) (ii) 15 cm (iii) 30 cm
11. Referring to the figure below, an image I is formed when an object is placed on the left hand side of a convex lens. Draw two light rays to locate the position of the object as O. Answer
12. In the following figure, sketch the refracted rays and locate the image (I). I Answer
13. An object (letter “P” card) which is 5 cm in height, is placed at 30 cm in front of a convex lens. A clear image is formed on the screen. The focal length of the lens is 20 cm. convex lens translucent screen (a) Is the image real or virtual? The image is real. Answer
(b) When a boy is at position (i) X and then (ii) Y, what will he see? b (i) If the boy is at position X, he will see a letter ___ (ii) If the boy is at position Y, he will see a letter ____. convex lens d translucent screen Answer
(c) Draw a ray diagram to determine the image distance and magnification. Use the scale shown in the figure. Answer 5 cm
6 x 10 cm = _____. 60 cm (c) Image distance = _____ Height of image 10 2 Magnification=───── =───= _______. 5 Height of object 5 cm
18. 3 Measuring the focal length of a convex lens Projecting the image of a distant object n Focal length = distance between the lens and the screen
Using a lens-mirror combination n Focal length = distance between the lens and the screen Experiment 18. 4
18. 5 The lens formula (REAL is POSITIVE)
Using the lens formula, do worked examples: 1, 3, 4, 5 and 9. 15 minutes
P. 4 Notes – 1 Negative sign Means that the image is virtual. The image distance is 30 cm.
The image’s size is 15 cm The image is virtual, erect and magnified.
P. 4 Notes – 3 The image distance is 30 cm.
P. 4 Notes – 4 The image is real, inverted and magnified. m = 60/30 = 2
P. 4 Notes – 5 The image is virtual, erect and magnified. m = 30/10 = 3
P. 4 Notes – 9 Magnification = v / u 6/2 = v/ u v = 3 u = 30 cm
Notes P. 14
P. 14 Notes v = -60 cm, f = 30 cm
P. 14 Notes m = 60/20 = 3 3 = hi / ho ho = 15/3 cm = 5 cm
P. 14 Notes The image is real, inverted and same size as object. m = 10/10 = 1
P. 15 Notes Convex lens Virtual, erect and magnified m = 40/8 hi = 5 x 2 cm = 10 cm Area of the image of stamp = 10 x 10 = 100 cm 2
Lens formula Book P. 202 Checkpoint 1, 3 P. 205 Exercise 1, 2, 5, 6, 8, 9
Checkpoint (p. 202) 1. (a) Positive (b) Negative (c) Positive (d) Negative
3. The image distance is 20 cm. Since the sign of v is negative, the image is virtual.
P. 205 Exercise 1. A. v = 30 cm f = 10 cm 2.
5. (a)The image distance is 30 cm. The linear = 2 magnification of the image is (b) Since v is positive, the image is real.
6. (a) The object distance is 16. 7 cm. The linear magnification of the image is = 1. 5. The height of the image is 2 × 1. 5 = 3 cm.
6 (b) The object distance is 7. 14 cm. The linear magnification of the image is = 3. 5. The height of the image is 2 × 3. 5 = 7 cm.
8. A sharp magnified image is formed. (a) The object distance is 12. 9 cm. The linear magnification of the image is = 3. 5.
(b)(i) a b b a The lens is moved by 45 − 12. 86 ≈ 32. 1 cm.
(b (ii) The linear magnification of the image is ≈ 0. 286.
9. (a) The data is tabulated below. (1/u) / 0. 167 0. 143 0. 125 0. 111 0. 100 cm− 1 (1/v) / 0. 164 0. 189 0. 208 0. 222 0. 233 cm− 1
(b) The y-intercept is 0. 337 cm− 1. The focal length f is ≈ 2. 97 cm.
Revision Book P. 173 Checkpoint 1, 3 P. 180 Checkpoint 1, 3 P. 188 Checkpoint 1, 2 (a) (b), 3 (a) (b) P. 189 Exercise 1, 3, 4, 5, 7, 8, 9, 10 P. 196 Checkpoint 1 - 4 P. 197 Exercise 3, 5, 6
P. 173 Check. Point 1. R 3. (a) (b) (c) Impossible Possible Impossible. Note that the rays should converge to a point on the focal plane and the ray passing through the optical centre will not be bent.
Checkpoint (p. 180) 1. A 2. The ray diagram is shown below. The height of the image is 4 cm. The image distance is 15 cm.
3.
P. 188 Checkpoint 1. A 2. (a) Incorrect. The image becomes larger as an object moves from 2 F to F. (b) Correct (c) Incorrect. A concave lens form virtual images only. (d) Incorrect
3. (a) The image is inverted, diminished and real.
(b) The image is erect, magnified and virtual.
P. 189 Exercise 1. A convex lens of focal length f is used as a magnifying glass. The object distance should be D. smaller than f
3. An image is formed by a convex lens. Which of the following statements about the image formed are correct? (1) Its nature depends on the object distance. (2) It must be erect. (3) It is formed on the focal plane if the object is placed at infinity. C. (1) and (3) only
5. The image is erect, magnified and virtual.
7. The focal length is 6 × 2 = 12 cm.
8. (a) (b) The image becomes dimmer.
9. (a) The image forms on the same side as the object. (b) Initially the object distance is smaller than the focal length. Now, the object distance is between the focal length and twice the focal length. Thus the image changes from erect to inverted and virtual to real.
10. (a) Lenses A and C are convex lenses. (b) Lens A has a larger focal length. (c) The nature does not change. (d) The nature does not change.
P. 196 checkpoints 1 - 4
1. height of the image height of linear the object magnification (a) (b) (c) 4 cm 8 cm (d) (e) (f) image distance object distance 2 5 cm 0. 5 40 cm 2 1 cm 6 cm 4 2. 67 cm 3 16 cm 0. 5 5 cm
2. An object is placed twice the focal length away from a convex lens. The linear magnification of the image is A. greater than 1. B. equal to 1. C. smaller than 1
3. The linear magnification of the image is 4 / 2 = 2
4. (a) The linear magnification of the image = = 1. 5. (b) The linear magnification of the image decreases. The object height is 4 cm
P. 197 Exercise 3, 5 , 6
3. An object of height 3 cm is placed 6 cm in front of a convex lens. A sharp image of 6 cm is caught by a screen placed on the other side of the lens. What is the image distance?
5. (a) The image is diminished. Since the lens used is convex, the image is also inverted and real. (b) The linear magnification of the image is 3/5 = 0. 6.
5. (c) The focal length of the lens is 7 cm.
6. (a) L 1 can form a real image and is thus a convex lens. (b)The linear magnification of the image is 2/3 = 0. 6667 ≈ 0. 667.
(c) Let v and u be the image distance and the object distance respectively. v + u = 50 (1) 1. 5 v = u (2) Substitute (2) into (1) u = 1. 5 × 20 = 30 cm. The image distance and the object distance are 20 cm and 30 cm respectively.
6 (d)
(e) (i) The focal length of L 2 is larger. (ii) The image is erect, magnified and virtual.
Revision Book P. 210 Chapter Exercise 1, 3, 4, 7, 8, 9, 10, 11, 12, 14, 17, 18, 19, 21, 22, 23
- Convex polygon examples
- Convex hull is the smallest convex set
- Convex vs concave
- Emetropy
- Perfect substitutes utility function
- Convex
- Convex and concave polygons
- Image formation by convex lens
- Convex mirror is a diverging mirror
- Ray tracing convex lens
- Humeroulnar joint concave convex
- What is polygons
- Tipus de poligons segons els costats
- Kanat tangwongsan
- Convex lens focal length
- Where is the proximal radioulnar joint
- Elements of morphology
- Convex 39m 60m
- Power of lens
- The rearview mirror should be checked
- Image formed by convex mirror when object is at infinity
- Uses of convex mirror
- Pole in polar coordinates
- Convex upward
- Polygon convexity
- Convex hull
- Convex optimization in machine learning javatpoint
- Diverging lens negative focal length
- Concave convex lens simulation
- Properties of convex lens
- Irregularities in population pyramids
- Poligon definitie
- What is the sum of the exterior angles of a decagon
- Geometric relationships
- Snell's law derivation class 10
- Cahaya adalah
- Concave vs convex polygon
- Convex hull collision detection
- Fresnel and fraunhofer diffraction
- Convex polygon formula
- Filled area primitives in computer graphics
- Convex shape image
- A lens that curve outwards and are fatter in the middle
- Mirror formula
- Convex hull
- Spherical mirror equation
- Curved
- Converging lens ray diagram
- Plane and curved mirrors
- Square trapezoid
- Polygon or not
- Concave lens in water
- Concave and convex mirror
- Convex limacon
- Convex population pyramid
- Flat limacon
- Convex optimization
- Image formation by convex lens
- Draw diagonal lines for each given polygon
- Convex octagon
- Convex vs concave lens
- Convex mirror salt
- Convex profile
- Salt reflection acronym
- Treatment plane
- Squareedge
- Polygons definition
- Uses of convex mirror
- Total internal reflection in daily life
- Thin lens equation for diverging lens
- Concave vs convex
- What is convex polygon
- Uses of concave mirror
- Convex lens thicker
- A concave heptagon
- Exact matrix completion via convex optimization
- Patrulater inscriptibil
- Convex vs concave teeth
- Concave st elevation
- Long-sightedness lens
- Flush weld symbol
- Mehran convex mirror
- Convex
- Lens ray diagram
- Bacteria margins
- Magnification equation lens
- Cataract
- What is a critical lens in literature
- Lenses graph analysis
- Diverging lens concave
- Sign convention for lenses in tabular form
- What are the different critical lenses
- The analysis of a literary text through various lenses
- Jet lenses review
- Contact lens advantages
- Physics classroom lenses and mirrors
- Ray diagrams gcse
- Refraction of light in lenses
- Literary criticism definition
- Types of camera lenses
- Types of camera lenses
- Physics of lenses
- Asanb
- Function of compound microscope
- Characteristics of a lens
- Critical lens
- Owl literary criticism
- "lenses.io"
- What are the four critical lenses
- The action of lenses depends mainly on
- Army ethical reasoning model
- Ethical lenses army
- Site:slidetodoc.com
- Morgan lens contraindications
- Lenses in literature
- 5 lenses of social studies
- Is nearsightedness reversible
- Interdisciplinary lenses