NCERT Solutions for Class 10 Science Chapter 9 – Light Reflection and Refraction
At the Orchids International School, we center our focus on the deep understanding of basic scientific concepts, and topics like Light Reflection and Refraction have found a place in our scheme of things. Our Class 10 Science Chapter 9 resource is one tool that will aid learning and bring clarity to tough concepts. With our Class 10 Science Chapter 9 PDF, a student may get to learn all principles associated with Light, Reflection, and Refraction at their own pace. Ensure to take note of each concept well enough. This chapter will explain what light does when it is allowed to fall over a variety of surfaces. We affirm that we continue to be committed to quality learning experiences that empower success in each and every child at Orchids International School.
Download PDF For NCERT Solutions for Science Light Reflection and Refraction
The NCERT Solutions for Class 10 Science Chapter 9 – Light Reflection and Refraction are tailored to help the students master the concepts that are key to success in their classrooms. The solutions given in the PDF are developed by experts and correlate with the CBSE syllabus of 2023-2024. These solutions provide thorough explanations with a step-by-step approach to solving problems. Students can easily get a hold of the subject and learn the basics with a deeper understanding. Additionally, they can practice better, be confident, and perform well in their examinations with the support of this PDF.
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Access Answers to NCERT Solutions for Class 10 Science Chapter 9 – Light Reflection and Refraction
Students can access the NCERT Solutions for Class 10 Science Chapter 9 – Light Reflection and Refraction. Curated by experts according to the CBSE syllabus for 2023–2024, these step-by-step solutions make Science much easier to understand and learn for the students. These solutions can be used in practice by students to attain skills in solving problems, reinforce important learning objectives, and be well-prepared for tests.
Light Reflection and Refraction
Find the speed of light in glass if the light enters from air to glass having a refractive index of c=3×108ms−1 .
What is the principal focus of a concave mirror?
The light rays parallel to the principal axis converge at a point on the principal axis after reflecting from the concave mirror.
The point of convergence on the principal axis of a concave mirror is called the principal focus of a concave mirror.
What is the focal length of a spherical mirror whose radius of curvature is 20cm?
It is given that, Radius of curvature of a spherical mirror,
R=20cm
It is known that, Radius of curvature is twice the focal length.
R=2f
⇒f=R/2
⇒f=20/2
⇒f=10cm
Therefore, the focal length of a spherical mirror with the radius of curvature equal to 20cm is f=10cm.
What is 1 diloptre of power of a lens?
Which mirror gives an erect and enlarged image of an object?
If the object is placed between pole and the principal focus of a concave mirror the image formed is virtual, erect and enlarged.
Erect and enlarged images are not possible in case of convex or plane mirrors.
Why is convex mirror preferred as a rear-view mirror in vehicles?
If the objects are placed in front of a convex mirror, then the image formed is an erect and diminished image.
In vehicles we need erect images and we need to see as many areas as possible behind the vehicles.
So, a convex mirror is preferred as a rear-view mirror in vehicles.
What is the focal length of a convex mirror whose radius of curvature is 32cm?
It is given that,
Radius of curvature of a convex mirror, R=32cm
It is known that, Radius of curvature is twice the focal length.
R=2f
⇒f=R/2
⇒f=32/2
⇒f=16cm
Therefore, the focal length of a convex mirror with the radius of curvature equal to 32cm is f=16cm.
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
-
A convex lens of focal length
-
50 cm
-
50 cm
-
A concave lens of focal length
-
50 cm
-
50 cm
-
A convex lens of focal length
-
5 cm
-
5 cm
-
A concave lens of focal length
-
5 cm
-
5 cm
a) When the object is placed between focus and optic centre, magnified and erect images are formed in a convex lens. So, while reading small letters a convex lens is preferred.
Find the location of image for a concave mirror that produces three times magnified (enlarged) real image of the object placed at 10cm in front of it.
It is given that,
Distance of object in front of mirror,
u=−10cm (negative sign due to the location of the object in front of the mirror)
Distance of image from mirror, v=?
It is known that, Magnification of a spherical mirror,
m= hi/ho= −v/u
where,
h/i is the height of the image
h/o is the height of the object
Let, ho=h
It is given that three times the enlarged real image of the object is produced.
So,
hi=−3h (− due to real image formation)
⇒m= −3h/h= −v/u
⇒3=v−10
⇒v=−30cm(negative sign due to the formation of inverted image)
Therefore, the location of image from the mirror is at a distance of 30cm and the nature of the image is inverted.
When a light ray travelling in the air enters obliquely into the water, how does it bend towards the normal or away from the normal? State reason.
When a light ray is travelling from the rarer medium to denser medium, it refracts towards the normal.
Here, the light ray bends towards the normal because the light ray is moving from air(rarer) to water(denser) medium.
From the table, find the medium having the highest optical density and the lowest optical density.
|
Material medium |
Refractive Index |
Material medium |
Refractive Index |
|
Air |
1.0003 |
Crown glass |
1.52 |
|
Ice |
1.31 |
Canada Balsam |
1.53 |
|
Water |
1.33 |
Rock salt |
1.54 |
|
Alcohol |
1.36 |
Carbon disulphide |
1.63 |
|
Kerosene |
1.44 |
Dense flint glass |
1.65 |
|
Fused quartz |
1.46 |
Ruby |
1.71 |
|
Turpentine oil |
1.47 |
Sapphire |
1.77 |
|
Benzene |
1.50 |
Diamond |
2.42 |
To find the materials of highest and lowest optical densities check for its refractive index. The one with the highest refractive index will have the highest optical density and the one with lowest refractive index will have the lowest optical density.
The highest optical density is for Diamond i.e., μ=2.42
The lowest optical density is for Air i.e. μ=1.0003
Among kerosene, turpentine oil and water in which medium does the light travel fastest? Refer to the table for refractive index.
|
Material Medium |
Refractive Index |
Material Medium |
Refractive Index |
|
Air |
1.0003 |
Crown Glass |
1.52 |
|
Ice |
1.31 |
Canada Balsam |
1.53 |
|
Water |
1.33 |
Rock Salt |
1.54 |
|
Alcohol |
1.36 |
Carbon Disulphide |
1.63 |
|
Kerosene |
1.44 |
Dense Flint Glass |
1.65 |
|
Fused Quartz |
1.46 |
Ruby |
1.71 |
|
Turpentine Oil |
1.47 |
Sapphire |
1.77 |
|
Benzene |
1.50 |
Diamond |
2.42 |
What is the meaning of the statement “The refractive index of diamond is 2.42”?
No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be
-
Plane
-
Concave
-
Convex
-
Either plane or convex
d) Erect images are produced by both plane and convex mirrors for objects at any position.
A spherical mirror and a thin spherical lens have each a focal length of −15cm . The mirror and the lens are likely to be
-
Both concave
-
Both convex
-
The mirror is concave and the lens is convex
-
The mirror is convex, but the lens is concave
a) For a concave lens the primary focus is on the same side as the object and is negative. In the case of a concave mirror, the focus is in front of the mirror and negative. Therefore, the mirror and lens are likely to be concave.
Image formed by a convex lens is real and inverted and at a distance of 50cm from the lens. Find the position of the needle in front of the convex lens when the image is equal to the size of the object. Also, calculate the power of the lens.
Therefore, the object distance from the lens is u=−50cm and power of the lens is P=+4D.
What is the power of a concave lens of focal length 2m?
Which one of the following materials cannot be used to make a lens?
-
Water
-
Glass
-
Plastic
-
Clay
d) Clay can’t be used to make a lens because it is opaque.
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should the position of the object be?
-
Between the principal focus and the centre of curvature
-
At the centre of curvature
-
Beyond the centre of curvature
-
Between the pole of the mirror and its principal focus.
d) The object is placed between the pole of the mirror and its principal focus when the image formed is virtual, erect and larger than the object in the concave mirror.
Where should an object be placed in front of a convex lens to get a real image of the size of the object?
-
At the principal focus of the lens
-
At twice the focal length
-
At infinity
-
Between the optical centre of the lens and its principal focus
b) An object should be placed at a distance of twice the focal length of a convex lens to get a real image of the size of the object.
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm
. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
To obtain an erect image in a concave mirror the object should be placed between Focus and the Optic centre.
Here, the focal length of the concave mirror is given as 15cm.
Therefore, the range of distance of the object from the mirror is from 0cm to 15cm.
The nature of the image is virtual.
The image is larger than the object.
A virtual, erect and magnified image is formed.
Name the type of mirror used in the following situations and support your answer with reason.
-
Headlights of a car
-
Side/Rear-View Mirror of a Vehicle
-
Solar Furnace
- In the headlights of a car, a concave mirror is used. Because in concave mirrors a parallel beam of light is produced if the bulb is placed at the focus.
- In a side/rear-view mirror of a vehicle , a convex mirror is used. Because when objects are placed in front of the convex mirror, erect and diminished images are formed which gives a wider field of view.
- In solar furnaces, Concave mirrors are used. They converge sunlight to a point and produce high temperatures because of their converging properties.
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Yes, the lens produces a complete image of the object with less intensity.
Consider the following two cases:
In the first case the lower half of the lens is covered with black paper. Light rays coming from the object are refracted only from the upper half and the image is formed, whereas in the lower half the light rays are blocked.
In the second case the upper half of the lens is covered with black paper. Light rays coming from the object are refracted only from the lower half and the image is formed, whereas in the upper half the light rays are blocked.
Therefore, change in intensity of the image is observed i.e., the intensity of the image is less and the complete image is formed.
An object of 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
It is given that,
Height of the object, ho=5cm
Distance of object in front of lens, u=−25cm
Distance of image from lens, v=?
As the magnification is −0.66, the negative sign indicates that the object is inverted and less than 1 indicates that the image is smaller than the object. Therefore, the position of the image is 16.66cm from the lens. The height of the object is 3.3cm. The nature of the image is real, inverted and diminished.
A concave lens of focal length 15 cm forms an image 10 cm from the lens. Find the distance of an object from the lens? Draw the ray diagram.
It is given that,
Focal length of the lens,
f=−15cm
Distance of image from lens,
v=−10cm
Distance of object in front of lens,
u=?
Thus, the object is at a distance of 30cm from the lens.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
It is given that,
Focal length of the convex mirror,
f=+15cm
Distance of object in front of convex mirror,
u=−10cm
Distance of image from convex mirror,
v=?
What does “The magnification produced by a plane mirror is +1” mean?
An object 5 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm . Find the position of the image, its nature and size.
It is given that,
Distance of object in front of the mirror,
u=−20cm
Distance of image from the mirror,
v=?
The radius of curvature of the mirror,
R=30cm
R=30cm
The focal length of the mirror,
f=?
f=?
It is known that,
Radius of curvature is equal to twice the focal length.
⇒R=2f ⇒30=2f
f=30/2 = 15cm
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm . At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.
It is given that,
Distance of object in front of mirror,
u=−27cm
Distance of image from the mirror,
v=?
Focal length of the mirror,
f=−18cm
From mirror formula:
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