Magnet Brains Notes Sample by pdlegands25

TOP IN YOUR EXAMS
WITH MAGNET BRAINS NOTES
From NCERT 6th to 12th With NCERT Exemplar
KEY HIGHLIGHTS
Visit Our Website: www.magnetbrains.com
❖ Chapter Wise Concept
❖ NCERT Solutions
❖ Multiple Choice Questions
❖ Chapter Wise Concept
❖ NCERT Solutions
❖ Multiple Choice Questions
❖ Most Important Questions
Class 9th to 12th
Class 6th to 8th
Note* - Notes will be provided only for those chapters whose videos are available.

● Overview
● Reflection of Light
Class 10th
- Physics
Light – Reflection
and Refraction
Notes Sample For
Class 6th to 12th
If you are class 10th student then you will get notes in this form*

➔ Reflection of light and laws of reflection.
➔ Characteristics of Images Formed by Plane
Mirror.
➔ Spherical mirror.
➔ Terms related to spherical mirrors.
➔ Sign conventions for spherical mirrors.
➔ Rules for tracing images formed by concave
mirror.
➔ Image formation by a concave mirror in
different positions of the object.
Overview:
CLASS 10th - PHYSICS - LIGHT-REFLECTION AND REFRACTION

➔ Mirror formula.
➔ Rules for tracing images formed by
convex mirror.
➔ Image formation by convex mirror.
➔ Magnification produced by spherical
mirrors.
➔ Uses of spherical mirrors.
➔ Refraction of light.
➔ Causes and Laws of refraction of light.
➔ Relative refractive index.
Overview:

➔ Refraction through a rectangular glass slab.
➔ Spherical lenses.
➔ Terms related to spherical lenses.
➔ Image formation by convex and concave lens.
➔ The new Cartesian sign conventions for
lenses.
➔ Lens formula.
➔ Linear magnification produced by lenses
➔ Power of lens.
➔ Power of combination of lenses.
Overview:

❖ Source
● A source of light is an object, from which light
is given out.
● Some sources of light are natural and many
others are man made sources.
● The source of light are of two kinds:
➔ Self luminous: A self luminous source is that
which possesses light of its own. For example;
the sun, the stars, electric lamps, candles etc.
are self luminous sources.
Reflection of Light:

➔ Non luminous: A non luminous source is that
which does not possess light of its own. It
receives light from an external source and
scatters it to the surrounding. For example; the
moon, a book, a table, a chair etc. are
non-luminous sources.

Self luminous sources of light

Non- luminous sources of light

❖ Medium
A medium is a substance through which light
propagates or tries to do so. There are three types
of media of light.
➔ Transparent: It is a medium through which
light propagates easily. For example; air,
water, glass etc. are transparent media.
➔ Translucent: It is a medium through which
light propagates partially. For example; paper,
ground, glass etc. are translucent media.

❖ Medium
➔ Opaque: Its is a medium through which light
cannot propagate. For example; wood, metals
etc. are opaque media.

Transparent media

Translucent media

Opaque media

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Reflection of Light
Class 10th
- Physics
Light–Reflection
and Refraction

❖ Reflection of light is the phenomenon of
bouncing back of light in the same medium on
striking the surface of any object.
When a ray of light approaches a smooth polished
surface and the light ray bounces back, it is called
the reflection of light.

➔ The ray which falls on the surface is called the
incident light ray.
➔ The ray that bounces back is known as the
reflected ray.
➔ If we draw a perpendicular on the reflecting
surface, at the point of incidence it is called the
normal.
➔ In reflection, path of light rays changes
without any change in medium.

❖ Types of reflection:
➔ Regular/ Specular Reflection: A smooth
surface, such as a mirror, a polished metal, or a
calm body of water, will reflect all the light that
arrives from a given direction at the same
angle. This reflection is known as regular or
specular reflection. The image formed is crisp
and clear.
All the rays of light that are reflected from a
surface are parallel if a parallel light source is
incident on it. Thus, a regular reflection produces
an image.

➔ Diffused Reflection: When light strikes rough
surfaces, it reflects in a diffuse manner. When
a beam of light strikes such a surface, it is
reflected at different angles and in all
directions. Depending on how rough their
surfaces are, the light that strikes the objects
in our room is diffused in all directions. This
reflection does not produce any image.

❖ Laws of Reflection-
➔ First law:
According to this law, the incident ray, the
reflected ray and the normal (at the point
of incidence), all lie in the same plane.
According to first law, AO, OB and ON, all
lie in the plane of the paper.
Neither of the two rays or normal goes
down into the paper or comes up out of
the paper.
A B
M M’
O
N

➔ Second law:
According to this law, the angle of
reflection (r) is always equal to the angle
of incidence (i).
Angle of incidence (i) is the angle, which
the incident ray makes with the normal to
the mirror.
Angle of reflection (r) is the angle, which
the reflected ray makes with the normal to
the mirror.
∠AON = i and ∠NOB = r
A B
M M’
O
N
i r

➔ Second law:
According to the second law, ∠i = ∠r
It means if ∠i = 60o
, then ∠r = 60o
And if ∠i = 30o
, then ∠r = 30o
Theses laws of reflection are applicable to all types of
reflecting surfaces including spherical surfaces.

➔ Second law:
Incident ray is along NO and reflected ray
is along ON.
∠i = 0
o
, ∠r = 0
o
∠i = ∠r
It means that a ray of light incident
normally on the mirror, retraces its path
on reflection.
∠i = ∠r
M M’
N
o

❖ Following are the Characteristics of Images Formed
by Plane Mirrors:
➔ The image of a real object is always virtual. Such an
image cannot be taken on a screen.
➔ The image formed in a plane mirror is always erect
i.e. upside of the object and vice - versa.
Characteristics of Images Formed by Plane Mirror:

Characteristics of Images Formed by Plane
Mirror:
➔ The size of image in a plane mirror is
always the same as the size of the
object.
➔ The image formed in a plane mirror is as
far behind the mirror, as the object is in
front of the mirror.
➔ The image formed in a plane mirror is
laterally inverted i.e. the left side of the
object becomes the right side of the
image and vice-versa.

NCERT Solutions
Class 10th
- Physics
Light–Reflection
and Refraction

NCERT Solutions (Page 168)
Question 1: Define the principal focus of a concave mirror.
Solution: Light rays that are parallel to the principal axis of a concave
mirror converge at a specific point on its principal axis after reflecting from
the mirror. This point is known as the principal focus of the concave mirror.

Question 2: The radius of curvature of a spherical mirror is 20 cm. What is
its focal length?
Solution: Radius of curvature, R = 20 cm
Radius of curvature of a spherical mirror = 2 x
Focal length (f)R = 2f
f = R/2 = 20/2 = 10
Hence, the focal length of the given spherical mirror is 10 cm.

Question 3: Name a mirror that can give an erect and enlarged image of an
object.
Solution: Concave Mirror
Question 4: Why do we prefer a convex mirror as a rear-view mirror in
vehicles?
Solution: We prefer a convex mirror as a rear - view mirror in vehicles
because it gives a wider field of view which allows the driver to see most of
the traffic behind him. Convex mirrors always form a virtual, erect, and
diminished image of the objects placed in front of it.

Question 5: Find the focal length of a convex mirror whose radius of
curvature is 32 cm.
Solution: Radius of curvature, R = 32 cm
Radius of curvature = 2 x Focal length (f)
R = 2ff = R/2 = 32/2 = 16
Hence, the focal length of the given convex mirror is 16 cm.

MOST IMPORTANT
QUESITONS
Class 10th
- Physics
Light–Reflection
and Refraction

Very Short Answer Type Questions:
Que. 1 What is the magnification of the images
formed by plane mirror and why?
Ans. Its magnification is +1 because plane
mirror always forms a laterally inverted image.
CLASS 10th
- PHYSICS - LIGHT-REFLECTION AND REFRACTION - MOST IMPORTANT QUESTIONS

Que. 2 What is the minimum distance between
an object and its real image in case of a concave
mirror?
Ans. Zero (0). When the object is at C.
CLASS 10th

Que. 3 When a light ray passes obliquely
through the atmosphere in an upward direction,
how does its path generally change?
Ans. Light will bend away from its normal
direction.
CLASS 10th

Que. 4 What makes things visible?
Ans. In a lighted room, when light falls on an
object, it gets either partially or completely
reflected. This reflected light when received by
our eyes, enables us to see things.
CLASS 10th

Que. 5 Explain why a ray of light passing
through the centre of curvature of a concave
mirror, gets reflected along the same path.
Ans. The ray passing through the centre of
curvature is incident to the mirror along its
normal so ∠i = ∠y = 0. Therefore, the ray
retrace its path.
CLASS 10th

Short Answer Type Questions:
Que. 6 List four characteristics of the image
formed by plan mirror.
Ans. Four characteristics of the image formed by
plane mirror:
i. It is always virtual and erect.
ii. Size of image is equal to that of the object.
iii. Image is formed at the same distance
behind the mirror as the object is in front of
the mirror.
iv. Image is laterally inverted.
CLASS 10th

Que. 7 An object is placed at a distance of 30 cm
in front of a convex mirror of focal length 15 cm.
Write four characteristics of the image formed
by the mirror.
Ans. Image is–
i. Virtual
ii. Erect
iii. Diminished
iv. Laterally invented
CLASS 10th

Detailed Answer:
Four properties of image formed by the given
convex mirror are:
i. Image is always erect.
ii. Small in size
iii. Virtual
iv. Always form behind the mirror between
focus and pole
CLASS 10th

Que. 8 An object is placed at a distance of 12 cm
in front of a concave mirror of radius of
curvature 30 cm. List four characteristics of the
image formed by the mirror.
Ans. Four properties of the image formed by the
given concave mirror of the object placed
between focus and pole of the mirror are :
I. Image is always erect.
II. Big in size
III. Virtual
IV. Always forms behind the mirror.
CLASS 10th

Que. 9 A ray of light is incident on a convex
mirror as shown. Redraw the diagram and
complete the path of this ray after reflection
from the mirror. Mark angle of incidence and
angle of reflection on it.
Ans.
Tracing the reflected ray
Marking ∠i % ∠r
CLASS 10th

Que. 10 The linear magnification produced by a spherical
mirror is +3. Analyse this value and state the (i) type of
mirror and (ii) position of the object with respect to the
pole of the mirror. Draw ray diagram to show the
formation of image in this case.
Ans. (i) Concave mirror
(ii) Between the pole and focus.
CLASS 10th

Long Answer Type Questions:
Que. 11
a. To construct a ray diagram we use two which are so
chosen that it is easy to know their directions after
reflection from the mirror. List two such rays and state
the path of these rays after reflection in case of
concave mirrors. Use these two rays and draw ray
diagram to locate the image of an object placed
between pole and focus of a concave mirror.
b. A concave mirror produces three times magnified
image on a screen. If the object is placed 20 cm in
front of the mirror, how far is the screen from the
object?
CLASS 10th

Ans. (a) (i) Listing of any two (out of four) rays and stating their path
after reflection from a concave mirror.
(ii) Ray diagram
Using these two rays for the ray diagram when the object is in between
the pole and the focus of the mirror.
(b) u = - 20 cm, m = - 3
m = v/-u
v = -m*(-u)
= -(-3)*(-20 cm) = -60 cm
Distance between the object and the screen is 40 cm
= -60 cm - (-20 cm) = -40 cm
CLASS 10th

Que. 12 One-half of a convex lens is covered with a
black paper. Will this lens produce a complete
image of the object? Verify your answers
experimentally. Explain your observations.
Solution: A point on the object needs only two rays
to form an image. Since the entire lens is not
covered, at least two rays from each point does
pass through the lens and hence, image is formed.
However, since the number of rays involved in the
image formation reduces as the lens is covered, the
image formed is of lesser intensity and less
brighter.
CLASS 10th

Experiment:
Apparatus needed: convex lens, candle, two black sheets of paper.
Procedure:
Mount a lens on a table. Light a candle with a match stick and place it on
one side of the lens on the table. Turn of the lights of the room so that it
gets dark. Take the sheet of paper and place it on the other side of the lens
as the candle. Now focus the image formed on the sheet of paper by
moving the sheet only. Observe the image. Mark the positions of candle,
lens and screen. Now, turn off the light. Take the lens and cover half of it
with the second sheet of black paper. Mount the lens on the table in the
original position and repeat the above experiment.
CLASS 10th

Observations:
A focussed image is obtained in both the experiments. However, the image
formed with half the lens covered is less bright as compared to when it is
uncovered.
CLASS 10th

MULTIPLE CHOICE
QUETIONS
Class 10th
- Physics
Light–Reflection
and Refraction

Que. The refraction of light is commonly kown as :
(a) Bending
(b) Scattering
(c) Reflection
(d) Interference
CLASS 10th
Multiple Choice Questions:

CLASS 10th
Que. What is the phenomenon of light coming back after hitting a smooth
plane surface called?
(a) Reflection
(b) Refraction
(c) Dispersion
(d) Splitting

CLASS 10th
Que. A lens is called a thin lens, if its overall thickness is :
(a) Small
(b) Large
(c) Infinitely large
(d) None of these

CLASS 10th
Que. A concave mirror forms the real image of an object which is magnified
4 times. The object is moved 3 cm away, the magnification of the image is 3
times. What is the focal length of the mirror?
(a) 3 cm
(b) 4 cm
(c) 12 cm
(d) 36 cm

CLASS 10th
Que. A concave mirror has a focal length of 20 cm. A real object is placed at
a distance of 20 cm from the pole of the mirror and in front oth the mirror.
The mirror produces an image at :
(a) Infinity
(b) 20 cm
(c) 40 cm
(d) 10 cm

Magnet Brains Notes Sample by pdlegands25

Magnet Brains Notes Sample by pdlegands25

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