Light- Reflaction and Refraction NCERT solution

Here we will discuss about the solution of the science ch1 class 10, light- reflection and refraction in-text as well as exercise solution.

In- text questions

Question 1.

Define the principal focus of a concave mirror?

Ans:- Principal focus is the point on principal Axis, where all the parllelly incident rays meet or where all the parllelly incident rays are converge.

Question 2.

The radius of curvature of a spherical mirror is 20 cm. what is its focal length?

Ans:- Given

         R= 20cm

 F= R/2

 F= 20/2 = 10cm

 

Question 3

Name a mirror that can give an erect an enlarged image of an object?

Ans:- Concave mirror, when we place object between principal focus and pole.

Question 4.

Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Ans:- We prefer a convex mirror as a rear view mirror in vehicles because it gives a wide range view as compared to other mirrors. Also we have to view whole scenario in a small piece of mirror which is possible with only convex mirror.

Question 5

Find the focal length of a convex mirror whose radius of curvature is 32 CM.

Ans:- Given,

         R= 32cm

         R=2f

         f= R/2

         = 32/2 = 16cm

Question 6

Concave mirror produces three times magnified real image of an object placed at 10 cm in front of it. Where is the image located?

Ans:- Given

       U= -10cm

       M= 3

M= -v/u

3= -v/-10

V= 3/10

V= +3.3 cm

Question 7

Are light travelling in air enters obliquely into water. Does the light re band towards the normal or away from the normal? Why?

Ans:- Towards the normal because refractive index of air is smaller than refractive index of water and as we all know that when light passes from rear to denser medium it bends towards the normal.

Question 8

Light enters from air to glass having refractive index 1.5. what is the speed of light in the glass?

Ans:- speed of light in vacuum (C)= 3*10^8 m/s

       n= C/V

       V= C/n

       V= 3*10^8/1.50

       =( 3/1.50)* 10^8 

       V= 2*10^8 m/s

Question 9

Find out the medium having highest optical density. Also find the medium with lowest optical density.

Ans:- Diamond have the highest optical density also called a refractive index. Air have the lowest optical density.

Question 10

You are given kerosene,turpentine, and water. In which of these does the light travel fastest?

Ans:- Water, having a refractive index of 1.33.

Question 11

The refractive index of a diamond is 2.42. what is the meaning of this statement?

Ans:- This statement means that the carbon have optical density of 2.42. also the amount of speed of light decreases in the diamond when it travels from other medium.

Question 12

Define 1 diopter of power of lens?

Ans:- When alliance having focal length of 1 m, it can be said that the power of the lens is 1 diopter.

Question 13

Find the power of a concave lens of focal length 2 m?

Ans:- Given

    f= -2m

    P= 1/f

    P= 1/-2

    P= -0.5