Long answer- Class 10 -Science-Physics-Chapter 10 – Light – Reflection and Refraction

Class 10 -Science-Long answer- Physics-Chapter 10 – Light – Reflection and Refraction

Q1. (a) Define real image of an object.

(b) Name the mirror that:

– can give real as well as virtual image of an object.

–  will always give virtual image of same size of an object.

– will always give virtual and diminished image of an object.

– is used by a doctor in examining teeth,

(b) With the help of a ray diagram explain the use of concave mirror as solar concentrators.

Ans :  a. When the reflected rays after reflection actually meet at a point then real image is formed.

b. Concave mirror

Plane mirror

Convex mirror

Concave mirror

c. The rays coming from the sun are parallel to principal axis and will concentrate at focus after reflection.

Q2. (a) Define absolute refractive index.

 (b) The path of a light ray from three different media A, B and C for a given angle of incidence is shown below. Study the diagrams and answer the following questions:

(i) Which of the three media A, B or C has maximum optical density?

(ii) Through which of the three media, will the speed of light be maximum?

(iii) Will the light travelling from A to B bend towards or away from the normal?

(iv) Will the refractive index of B relative to C be more than unity or less than unity?

Ans:

(a) Absolute refractive index of a medium is the ratio of speed of light in air/vacuum to the speed of light in medium.

(b) (i) Angle of refraction in medium C is minimum. Hence medium C is maximum optical denser.

(ii)  In least denser medium i.e. A the speed of light will be maximum.

(iii) Towards normal

(iv) Less than 1

Q3. Draw the ray diagram in each case to show the position, nature of image formed when the object is placed:

a. at the centre of curvature of a concave mirror

b. within focal length of a convex lens

c. between pole and focus of concave mirror

d. in front of concave lens

e. in front of convex mirror

Ans: