NCERT (CBSE)
Guide - Science Physics
Class X, LIGHT
- REFLECTION AND REFRACTION
NCERT Physics (Science) – CBSE Class 10 Notes, Study Materials
(LESSON 3 of 3)
Light –
Reflection and Refraction:
Image Formation
by a Convex Lens
(Table followed by figures)
|
|
Position of
the object
|
Position of
the image
|
Size of image
|
Nature of
image
|
|
1
|
At infinity
|
At focus F2
|
Highly
diminished, point sized
|
Real,
inverted
|
|
2
|
Beyond 2F1
|
Between F2 and 2F2
|
Diminished
|
Real,
inverted
|
|
3
|
At 2F1
|
At 2F2
|
Same size
|
Real,
inverted
|
|
4
|
Between F1 and 2F1
|
Beyond 2F2
|
Enlarged
|
Real,
inverted
|
|
5
|
At focus F1
|
At infinity
|
Infinitely
large or highly enlarged
|
Real,
inverted
|
|
6
|
Between focus
F1 and optic center O
|
On the same
side of the lens as the object
|
Enlarged
|
Virtual,
erect
|
Image Formation
by a Concave Lens
(Table followed by figures)
|
|
Position of
object
|
Position of
image
|
Size of image
|
Nature of
image
|
|
1
|
At the
infinity
|
At focus F1
|
Highly
diminished, point-sized
|
Virtual,
erect.
|
|
2
|
Between
infinity and optical center of the lens
|
Between focus
F1 and optical center O.
|
Diminished
|
Virtual,
erect.
|
Sign Convention
(Spherical Lenses)
The following
table summarizes the New Cartesian Sign Convention for spherical lenses:
|
Lens
|
Distance of
object (u)
|
Distance of
image (v)
|
Focal length
(f)
|
Height of object
|
Height of
image
|
||
|
Real image
|
Virtual image
|
Real image
|
Virtual image
|
||||
|
Convex
|
– ve
|
+ ve
|
– ve
|
+ ve
|
+ ve
|
– ve
|
+ ve
|
|
Concave
|
– ve
|
|
– ve
|
– ve
|
+ ve
|
|
+ ve
|
CCE Type CBSE Sample
Questions
Q.1:
What are the differences between a spherical mirror and a lens?
Ans: The
differences between a spherical mirror and a lens are listed below:
Spherical
Mirror
- In a spherical mirror image is formed by reflection of light.
- t has a single focus.
- The center of the spherical mirror is known by the term Pole.
Spherical Lens
- Here image is formed by refraction of light.
- It has two foci.
- The center of the spherical mirror is known by the term Optical Center.
Q.2:
For which colour the refractive index of material is the maximum?
Ans: For violet
colour the refractive index of material is the maximum.
Q.3:
Will there be any change in focal length of a concave mirror or concave lens
when it is dipped in water?
Ans: No,
because the focal length is independent of the refractive index of the material
of mirror (or lens) and surrounding medium.
Q.4:
When light undergoes refraction, what happens to its wavelength, frequency?
Ans: Wavelength
of light decreases on entering a denser medium and increases on entering a
rarer medium. Frequency of light will remain same.
Q.5:
What is the focal length of a plane mirror?
Ans: It is
infinity, as the plane mirror is considered to be part of a spherical mirror
whose radius is infinite.
Q.6:
What is the magnification produced by a plane mirror?
Ans: The
magnification produced by a plane mirror is +1.
Q.7:
What is the emergent angle of light after refraction in a glass slab?
Ans: The
direction of the light after refraction in a glass slab will be parallel to the
incident ray of light. Hence, the emergent angle will be equal to the angle of
incidence.
Q.8:
Magnification (m) of a plane mirror is +1. What does 1 and +ve sign signify?
Ans: m = +1
signify that image is erect, virtual and of equal size.
Q.9:
Why is convex lens used in magnifying glass? Or, What is magnifying glass?
Ans: A
magnifying glass is used to read small prints or see very small things. A
convex lens produces virtual, erect and magnified image of an object when it is
placed close to the lens. Because of this property of the convex lens it is
used in magnifying glass to view magnified image of the objects.
Q.10:
Why a concave lens is called diverging lens?
Ans:
Fig: Diverging Lens
When a beam of
light parallel to the principal axis falls on a concave lens then they appear
to be diverging from a single point, also known as principal focus (F) of the
lens. Therefore, a concave lens is also known as Diverging Lens.
Further Study on
Chapter 10, Light - Reflection and Refraction
- Class 10 CBSE Physics (Science) | Light - Reflection And Refraction | Ncert Solutions – Science Textbook In-Text Questions
- Solutions of NCERT Class X, Light - Reflection and Refraction | 10th CBSE Guide for Physics (Science) | NCERT Solutions (Textbook Exercise)
- CCE type Multiple Choice Questions (MCQ) | Class 10, Solutions of NCERT (CBSE) Science (Physics) Light - Reflection and Refraction
- CBSE Hot Questions - NCERT Science Questions Bank | Class X Physics (Science) | Light: Reflection and Refraction
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