Chapter 3 physics
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The document summarizes key concepts about reflection of light by different surfaces including mirrors and lenses. It defines important terminology used to describe reflection such as focal length, radius of curvature, angle of incidence, and angle of reflection. Examples are given of the different types of images - real, virtual, enlarged, diminished - formed by concave and convex mirrors depending on the position of the object. Multiple choice questions are also provided to test understanding of these concepts.
![CHAPTER 3
Reflection of Light by Different Surfaces
Summary:
Light travels in a straight line.
When light reflected from a surface,
The angle of reflection = equal to the angle of incidence.
The incident ray, the normal at the point of incidence and the reflected
ray all lie in the same plane.
1/𝑓 = 1/𝑢 + 1/𝑣 or 𝑓 = 𝑢𝑣/(𝑢 + 𝑣)
Magnification = m = Size of the image /size of the object
OR = - Image distance/ Object distance = -v/u
Points to remember:
• The centre of sphere to which a spherical mirror belongs, is called centre of curvature.
• The geometric centre of the mirror is pole(P) of the mirror.
• The line which passes through the centre of curvature and pole is called Principal axis.
• The rays which are parallel to the principal axis of a concave mirror on reflection meet
at focus or focal point.
• The distance between pole and centre of curvature is Radius of curvature.
• The distance between pole and focus is called focal length.
• The relation between focal length and radius of curvature is given by R = 2f
• The relation between the angle of incidence and angle of reflection is given by First law
of reflection.
• Light selects the least time path to travel between two points. This principle was stated
by Fermat.
Multiple Choice questions:
1. If an object is placed at C on the principal axis in front of a concave mirror, the
position of the image is [ ]](https://image.slidesharecdn.com/chapter3physics-190422061650/85/Chapter-3-physics-2-320.jpg)
![a) at infinity b) between F and C c) at C d) beyond C
2. We get a diminished image with a concave mirror when the object is placed [ ]
a) at F b) between the pole and F c) at C d) beyond C
3. We get a virtual image in a concave mirror when the object is placed [ ]
a) at F b) between the mirror and F c) at C d) beyond C
4. Magnification m = [ ]
a) v/u b) u/v c) ho / hi d) hi /ho
5. A ray which seems to be travelling through the focus of a convex mirror passes
after reflection [ ]
a) parallel to the axis b) along the same path in opposite direction
c) through F d) through C
6. The angle of refraction of a light ray is the angle between [ ]
a) Incident ray and normal b) Refracted ray and normal c) Incident ray and
refracted ray d) refracted ray and interface separating two media.
7. A virtual, erected image is formed when an object is placed on the principal axis
of a convex lens [ ]
a) Beyond the centre of curvature b) At the centre of curvature
c)between centre of curvature and focus d) Between focal point and pole.
8. An image is formed at distance of 60 cm from the centre of a convex lens.
When the object distance is 30 cm, the focal length of the lens in cm is [ ]
a) 90 b) 20 c) 2 d) 0.05
9. The no of focal points, that every lens has [ ]
a) 4 b)3 c) 2 d) 1
10. Read the following two statements and pick the correct option [ ]
1) The virtual image can be captured on a screen](https://image.slidesharecdn.com/chapter3physics-190422061650/85/Chapter-3-physics-3-320.jpg)
![2) The real image can be captured on a screen
a) Only 1 is true b) Only 2 is true c) Both 1 and 2 are true
d) Both 1 and 2 are false.
11. When the object is at focus of a concave mirror, the image is formed at
[ ]
a) within focus b) Infinity c) Centre of curvature
d) Focus
12. The mirror used by dentists is [ ]
a) Concave b) Plane c) Convex d) Plane or concave
KEY
1. c 2. d 3. b 4. d 5. b 6.b 7. d 8. b 9. c 10. b
11. b 12. a](https://image.slidesharecdn.com/chapter3physics-190422061650/85/Chapter-3-physics-4-320.jpg)
Chapter 3 physics
- 1. AP POLYCET 2018 STUDY MATERIAL FOR PHYSICS(EM) SBTET, AP, AMARAVATI
- 2. CHAPTER 3 Reflection of Light by Different Surfaces Summary: Light travels in a straight line. When light reflected from a surface, The angle of reflection = equal to the angle of incidence. The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane. 1/𝑓 = 1/𝑢 + 1/𝑣 or 𝑓 = 𝑢𝑣/(𝑢 + 𝑣) Magnification = m = Size of the image /size of the object OR = - Image distance/ Object distance = -v/u Points to remember: • The centre of sphere to which a spherical mirror belongs, is called centre of curvature. • The geometric centre of the mirror is pole(P) of the mirror. • The line which passes through the centre of curvature and pole is called Principal axis. • The rays which are parallel to the principal axis of a concave mirror on reflection meet at focus or focal point. • The distance between pole and centre of curvature is Radius of curvature. • The distance between pole and focus is called focal length. • The relation between focal length and radius of curvature is given by R = 2f • The relation between the angle of incidence and angle of reflection is given by First law of reflection. • Light selects the least time path to travel between two points. This principle was stated by Fermat. Multiple Choice questions: 1. If an object is placed at C on the principal axis in front of a concave mirror, the position of the image is [ ]
- 3. a) at infinity b) between F and C c) at C d) beyond C 2. We get a diminished image with a concave mirror when the object is placed [ ] a) at F b) between the pole and F c) at C d) beyond C 3. We get a virtual image in a concave mirror when the object is placed [ ] a) at F b) between the mirror and F c) at C d) beyond C 4. Magnification m = [ ] a) v/u b) u/v c) ho / hi d) hi /ho 5. A ray which seems to be travelling through the focus of a convex mirror passes after reflection [ ] a) parallel to the axis b) along the same path in opposite direction c) through F d) through C 6. The angle of refraction of a light ray is the angle between [ ] a) Incident ray and normal b) Refracted ray and normal c) Incident ray and refracted ray d) refracted ray and interface separating two media. 7. A virtual, erected image is formed when an object is placed on the principal axis of a convex lens [ ] a) Beyond the centre of curvature b) At the centre of curvature c)between centre of curvature and focus d) Between focal point and pole. 8. An image is formed at distance of 60 cm from the centre of a convex lens. When the object distance is 30 cm, the focal length of the lens in cm is [ ] a) 90 b) 20 c) 2 d) 0.05 9. The no of focal points, that every lens has [ ] a) 4 b)3 c) 2 d) 1 10. Read the following two statements and pick the correct option [ ] 1) The virtual image can be captured on a screen
- 4. 2) The real image can be captured on a screen a) Only 1 is true b) Only 2 is true c) Both 1 and 2 are true d) Both 1 and 2 are false. 11. When the object is at focus of a concave mirror, the image is formed at [ ] a) within focus b) Infinity c) Centre of curvature d) Focus 12. The mirror used by dentists is [ ] a) Concave b) Plane c) Convex d) Plane or concave KEY 1. c 2. d 3. b 4. d 5. b 6.b 7. d 8. b 9. c 10. b 11. b 12. a