# NCERT Solutions for Class 10 Science Chapter 10

NCERT Solutions for Class 10 Science Chapter 10 Light – Reflection and Refraction all intext questions given on Page 168 or Page 171 or Page 176 or Page 184 or Exercises in English and Hindi Medium free. Download all answers in PDF file format or download Offline apps 2020-2021 to use all the contents offline without internet. UP Board students are also using NCERT Textbook for their final exams. So, 10th Science chapter 10 question answers are useful for UP Board students also. Download here the UP Board Solutions for Class 10 Science Chapter 10 given on पेज 185 or पेज 188 or पेज 194 or पेज 203 or अभ्यास के प्रश्न उत्तर in हिंदी माध्यम to view online or download free in PDF format.

Important questions and CBSE previous years board questions related to chapter 10 are given with answers. All NCERT Solutions as well as Offline Apps are based on latest NCERT Books 2020-21 following the latest CBSE Syllabus 2020-2021.

## NCERT Solutions for Class 10 Science Chapter 10

 Class: 10 Science (English and Hindi Medium) Chapter 10: Light – Reflection and Refraction

### 10th Science Chapter 10 Answers in English & Hindi Medium

NCERT Solutions for Class 10 Science Chapter 10 Light – Reflection and Refraction all the question answers of intext questions as well as chapter end exercises are given below updated for 2020-21. NCERT solutions 2020-21 for class 10 other subjects are also in PDF as well as online to use.

### Class 10 Science Chapter 10 Solutions Related Pages

##### List four properties of the image formed by a plane mirror.

Properties of images formed by a plane mirrors:
(i) The image formed by a plane mirror is virtual and erect.
(ii) It is of the same size as the object.
(iii) The image is formed as far behind the mirror as the object is in front of it i.e., u = v.
(iv)It is laterally inverted i.e., image is inverted sideways with respect to the object.

##### List the four properties of the image formed by a convex mirror.

Properties of the image formed by a convex mirror:
(i) This image is always virtual and erect.
(ii) The image is highly diminished or point sized.
(iii) It is always formed between F and P.
(iv) As the object is moved towards the pole of convex mirror, image also moves towards its pole and gradually increases size till its size becomes almost equal to that of the object.

##### State the laws of refraction of light.

Laws of refraction of light: The refraction of light obeys the following two laws:
First law: The incident ray, the refracted ray and normal to the surface of separation at the point of incidence, all lie in the same plane.
Second law: The ratio of the sine of the angle of incidence and the sine of the angle of refraction is constant for a given pair of media. Mathematically,
[sin i] / [sin r] = n (a constant).
The ratio n2 is called refractive index of the second medium with respect to the first medium. The second law of refraction is also called Snell’s law of refraction.

##### What is meant by refraction of light?

Refraction of light: The phenomenon of bending of light from its straight line path as it passes obliquely from one transparent medium to another is called refraction of light.
The path of the ray of light in the first medium is called incident ray.
The path of the ray of light in the second medium is called refracted ray.
The angle between the incident ray and the normal at the surface of separation is called angle of incidence (i).
The angle between the refracted ray and the normal at the surface of separation is called angle of refraction (r).

#### Questions for Practice

Question 1:
Give three points of difference between real and virtual images.
Real Image:
(i) Here the rays actually meet at the image point.
(ii) It can be taken on a screen.
(iii) It is always inverted
Virtual Image:
(i) Here the rays appear to diverge from the image point.
(ii) It cannot be taken on a screen.
(iii) It is always erect.

Question 2:
Distinguish between a concave and convex lens.
Convex lens
(a) It is thicker at the centre than at the edges.
(b) It converges a parallel beam of light on refraction through it.
(c) It has a real focus.
Concave lens:
(a) It is thinner at the centre than at the edges.
(b) It diverges a parallel beam of light on refraction through it.
(c) It has a virtual focus.

##### Questions from Board Papers

Question 1:
Define the principal focus of a concave mirror. Calculate the focal length of the mirror of radius of curvature of 20 cm.
The principal focus of concave mirror is a point on its principal axis at which a beam of light parallel to the principal axis actually converges after reflection from the mirror.
Focal length = R/2 = 20/2 = 10 cm.

Question 2:
State the type of mirror preferred as
(i) rear view mirror in vehicles,
(ii) shaving mirror. Justify your answer giving two reason in each case.
(i) A convex mirror is preferred as a rear-view mirror because
(a) It always forms an erect, virtual and diminished image of an object placed anywhere in front of it.
(b) It has wider field of view.
(ii) A concave mirror is preferred as a shaving mirror because when it is held closer to the face, it form:
(a) an enlarged image of the face
(b) an erect image of the face

### Important Questions on 10th Science Chapter 10

Define the principal focus of a concave mirror.
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.
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Radius of curvature, R = 20 cm
Radius of curvature of a spherical mirror = 2 × Focal length (f)
R = 2f
f = r/2 = 20/2 = 10 cm
Hence, the focal length of the given spherical mirror is 10 cm.
Name the mirror that can give an erect and enlarged image of an object.
When an object is placed between the pole and the principal focus of a concave mirror, the image formed is virtual, erect, and enlarged.
Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Convex mirrors give a virtual, erect, and diminished image of the objects placed in front of them. They are preferred as a rear-view mirror in vehicles because they give a wider field of view, which allows the driver to see most of the traffic behind him.
A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
The light ray bends towards the normal.
When a ray of light travels from an optically rarer medium to an optically denser medium, it gets bent towards the normal. Since water is optically denser than air, a ray of light travelling from air into the water will bend towards the normal.
The refractive index of diamond is 2.42. What is the meaning of this statement?
Refractive index of a medium nm is related to the speed of light in that medium v by the relation:

n = c/v

Where, c is the speed of light in vacuum/air
The refractive index of diamond is 2.42. This suggests that the speed of light in diamond will reduce by a factor 2.42 compared to its speed in air.

Define 1 dioptre of power of a lens.
Power of lens is defined as the reciprocal of its focal length. If P is the power of a lens of focal length F in metres, then

P = 1/f

The S.I. unit of power of a lens is Dioptre. It is denoted by D.
1 dioptre is defined as the power of a lens of focal length 1 metre.
1 D = 1 per meter                           