NCERT Class 10 Science Chapter 10 Light Reflection and Refraction Extra Questions and Answers
Class 10 Science Chapter 10 Extra Inside Questions and Answers – Light Reflection and Refraction. Here in this Page Class X Students can Learn Extra Questions & Answer 10th Chapter Science fully Inside.
We Provided Here Light Reflection and Refraction Science Chapter 10 Long Answer Type Question, Multiple Choice Questions & Answer, Short Answer Type Questions (2 or 3 marks), and Very Short answer Type Question (1 marks) Solution.
Class 10 Science Chapter 10 Extra Question with Answer – Light Reflection and Refraction
Science Chapter 10 Light Reflection and Refraction Class 10 Inside 5 Marks, 3 marks, 2 Marks & And 1 Marks Important Questions and Answers.
1.) Fill in the blanks.
1.) The spherical mirror with reflecting surface is curved _________ is called as concave mirror.
Ans:The spherical mirror with reflecting surface is curved inwards is called as concave mirror.
2.) The centre of the reflecting surface of spherical mirror is called as ________.
Ans: The centre of the reflecting surface of spherical mirror is called as pole P of the mirror.
3.) Convex lens is also called as______.
Ans: Convex lens is also called as converging lens.
4.) Concave lens is also called as______.
Ans: Concave lens is also called as diverging lens.
5.) The _______ mirrors are used due to their high converging property to generate large amount energy from sunlight.
Ans:The concave mirrors are used due to their high converging property to generate large amount of energy from sunlight.
6.) Focal length of concave mirror is _______ while the focal length of convex mirror is ______.
Ans:The focal length of concave mirror is negative while the focal length of convex mirror is positive.
7.) If magnification m is negative then image formed will be____.
Ans:If the magnification is negative then image formed will be real.
8.) The SI unit of power of lens is ____.
Ans:The SI unit of power of lens is dioptres.
2.) Multiple choice questions:
1.) The relation between radius of curvature and focal length of the spherical mirror is
a) R=f/2
b) f= R/2
c) f=2R
d) R= 2f
Ans: d) R= 2f
2.) The power of spherical lens is given by
a) P= 1/2f
b) f=1/P
c) P= 1/f
d) P= 2f
Ans: c) P= 1/f
3.) If the value of magnification factor is +1 then the size of image will be
a) greater than size of object
b) less than size of object
c) equal to the size of the object
d) a and b
Ans: c) equal to the size of the object
4.) If the object is placed at the centre C of the concave mirror then the image will be formed at
a) at focus F
b) beyond centre C
c) in between F and C
d) at centre C
Ans: d) at centre C
5.) If more is the refractive index of the medium then more is the
a) speed of light through that medium
b) mass density of medium
c) optical density of the medium
d) none
Ans: c) optical density of the medium
6.) If the refractive index of benzene, rock salt and diamond are 1.5, 1.54 and 2.42 then in which medium the speed of light is more.
a) diamond
b) benzene
c) rock salt
d) not calculated
Ans: b) benzene
Because, less is the refractive index rarer is the optical medium and hence speed of light is more in that medium.
7.) Microscopes uses which type of lenses
a) concave lens
b) convex lens
c) plano-concave
d) biconcave
Ans: a) convex lens
3.) Very short answer questions.
1.) What is the nature of an image formed by the plane mirror and where the object is to be placed?
Ans:
When the object is placed in front of the plane mirror then the image will be formed behind the mirror which virtual, erect and its size is equal to the size of the object.
2.) What is mirror formula?
Ans:
The mirror formula is the relation between object distance u, image distance v and the focal length f of the mirror which is given by
1/f = 1/v + 1/u
3.) Give the magnification formula of mirror in terms of height of object and image.
Ans:
If h1 is the height of object and h2 is the height of the image then the magnification of the mirror m is given by,
Magnification= m= h2/h1
4.) If the radius of curvature of the concave mirror is 5cm find its focal length.
Ans:
Given that,
For concave mirror:
R= 5cm
We know that,
R= 2f
Thus, f= R/2 = 5/2= 2.5cm
5.) If the focal length of the concave lens is 10m find its power.
Ans:
Given that,
For concave lens:
Focal length f= -10m
Hence, the power of lens is given by,
P= 1/f = 1/-10= -0.1D
6.) If the object is placed at the focus of the concave mirror then where is the image formed?
Ans:
If the object is placed at the focus F of concave mirror then image will be formed at infinity which is highly enlarged, real and inverted as shown in figure below.
4.) Short answer questions:
1.) What is the mirror formula and define each term in it.
Ans:
- The relationship between focal length f, object distance u and the image distance v in case of spherical mirror is called as the mirror formula.
- It is given by,
1/f = 1/u + 1/v
Where,
- f is the focal length, the distance of principal focus F from the pole P of the spherical mirror is called as focal length of the spherical mirror.
- u is the object distance, the distance of the object from the pole of the spherical mirror is called as object distance.
- v is the image distance, the distance of the image from the pole of the spherical mirror is called as the image distance.
2.) What is optical density and how we can decide the optical density of the medium from its refractive index.
Ans:
- We know that, the ability of the medium to refract the light incident in it is called as the optical density of the medium.
- As the refractive index of the medium is more which means the optical density is more and the medium acts as the optical denser medium.
- While the medium having low refractive index has low optical density which means the medium acts as the optically rarer medium.
- Thus, we can decide the optical density of the medium from the refractive index.
3.) What is the speed of light in a medium with more refractive index and in a medium with lower refractive index.
Ans:
- As the refractive index of the medium is greater which means it is optically denser medium and hence the speed of light in that medium is less.
- While the medium with lower refractive index has low optical density which means it is optically rarer medium and hence speed of light in that medium is more.
4.) Why speed of light in water is less than speed of light in air.
Ans:
- As we know that, the refractive index of water is more than refractive index of air. Hence, water is optically denser medium than air.
- Due to which the speed of light in air is greater than the speed of light in water.
5.) If the focal length of concave lens is 20cm and image distance is 15cm then find the object distance.
Ans:
Given that,
For concave lens:
Focal length f= -20cm
Image distance v= -15cm
By lens formula,
1/f = 1/v – 1/u
Thus, 1/u = 1/v – 1/f
1/u = 1/-15 – 1/-20
1/u = -1/15 + 1/20
1/u = (-20+15)/300
1/u = -5/300
Thus, u = -300/5
Hence, u= -60 cm
Thus, the object distance will be found as 60 cm.
In case you are missed :- Previous Chapter Extra Questions
6.) What happens when a ray of light is incident parallel to principal axis of concave and convex mirror with ray diagram.
Ans:
When a ray of light is incident parallel to principal axis of a concave mirror then after reflection the ray of light goes through principal focus of the concave mirror as shown in figure.
- When a ray of light is incident parallel to the convex mirror then after reflection the it will appear to diverge from the principal focus of the convex mirror as shown in figure.
5.) Long answer questions:
1.) Explain the following terms.
a) pole of the spherical mirror
b) centre of curvature of the spherical mirror
c) radius of curvature of spherical mirror
d) principal focus of spherical mirror
Ans:
a)
Pole of the mirror:
- Pole of the spherical mirror is the centre point on the reflecting surface of spherical mirror.
- It is denoted by P.
b)
Centre of curvature of the mirror:
- The spherical reflecting surface has its own centre I.e. the centre of sphere which is termed as the curvature of the spherical mirror.
- It is denoted by C.
c)
Radius of curvature of the mirror:
- Radius of curvature is the radius of the spherical reflecting surface forming the spherical mirror.
- It is denoted by R.
d)
Principal focus of the mirror:
- When the beam of parallel rays is incident on the reflecting surface of a concave mirror then after reflection all these rays meet at single point on the principal axis and that point is called as the principal focus of the concave mirror.
- It is denoted by F.
2.) What happens in following cases explain with ray diagram
a) when a ray of light is passed through the optical centre of concave and convex lens
b) when a ray of light is passed through the focus of the convex and concave lens
Ans:
a)
- When ray of light is passed through the optical centre of the concave and convex lens then after reflection the ray emerges out without deviation as shown in following figure.
Fig. convex mirror
Fig. concave mirror
b)
- When a ray of light is passed through focus of the convex lens then after reflection it emerges parallel to the principal axis as shown in figure.
- While when a incident ray of light appearing to meet the focus then after reflection it emerges as a ray parallel to principal axis as shown in following figure.
3.) Complete the following table with appropriate answers for concave mirror.
Position of the object | Position of the image | Size of the image | Nature of the image |
At infinity | Highly diminished and point size | Real and inverted | |
At centre of curvature C | Same size | Real and inverted | |
At focus F | At infinity | Real and inverted | |
Between pole P and focus F | Behind the mirror | enlarged |
Ans:
Position of the object | Position of the image | Size of the image | Nature of the image |
At infinity | At the focus F | Highly diminished and point size | Real and inverted |
At centre of curvature C | At centre of curvature C | Same size | Real and inverted |
At focus F | At infinity | Highly enlarged | Real and inverted |
Between pole P and focus F | Behind the mirror | enlarged | Virtual and erect |
4.) Identify the following figure and give their names and give one use of each.
Ans:
a)
The above figure shows the convex mirror which are mostly used in vehicles to see the vehicles at a distance apart from it behind the vehicle.
b)
The above figure shows the concave mirror which are used in parlours and as a shaving mirrors to see large image of the face in the mirror.
c)
The above figure shows the concave lens which are mainly used to diverge the incident rays and these lenses are used in telescopes, cameras, flashlights and also in eyeglasses.
d)
The above figure shows the convex lens which are used in magnifying glasses, cameras and in eyeglasses also.
5.) Draw the ray diagram for following conditions and give nature of images formed.
a) when the object is placed at the centre of the convex lens.
b) when placed between focus and optical centre of the convex lens
c) when the object is placed between centre and focus of the concave mirror
Ans:
a)
when the object is placed at the centre C1 of the convex lens then the image will be formed at the centre C2 on another side of convex lens which is real, inverted and of the same size as shown in figure below.
b)
when the object is placed between optical centre O and focus F1 of the convex mirror then the image will formed on the same side of the lens of the object and which is enlarged, virtual and erect as shown in figure bellow.
c)
when the object is placed between centre C and focus F of the concave mirror then the image will be formed beyond C and which is enlarged, real and inverted as shown in figure below.
6.) The object of height 5cm is placed in front of convex lens having focal length 15cm. The object is placed at a distance of 20cm from the convex lens. State nature of the image by finding magnification of convex lens.
Ans:
Given that,
For convex lens:
Object height h1= 5cm
Focal length f= +15cm
Object distance u= -20cm
We know that, lens formula is given by
1/f = 1/v – 1/u
Thus, 1/v = 1/f + 1/u
1/v = 1/15 – 1/20
1/v = (20-15)/300 = 5/300
Thus, v = 300/5= 60cm
Thus image will be formed at a distance of 60cm on the other side of the optical centre of the convex lens.
Hence, the image formed will be real and inverted.
Magnification of lens is given by,
m= h2/h1 = v/u
h2/5= -60/-20
h2= -15cm
And m= v/u = 60/-20= -3
Thus, the image formed will be real, inverted and enlarged.
In case you are missed :- Next Chapter Extra Questions