light - Reflection and Refraction class 10 P*01

1)Define light?
ans-Light is a form of energy .it brings the sensation of sight .it is a form of electromagnetic radiation. it also provide us means of communication.
2)Define beam of light?
ans-a bundle of rays originating from the same source of light in a particular direction is called a beam of light.
3)Define Parallel beam?
ans-when the race which constitutes the beam are parallel to one another then it is called a parallel beam of light.
4)Define convergent beam?
ans-when the rays are actually meet or appear to meet at a point then the beam containing such race are called convergent beam and rays are called convergent rays.
5)Define reflection?
ans-when light falls on a surface and gets back into the same medium it is called reflection .a highly polished surface or mirror reflects the light.
6)Define Image?
ans-the point of convergence for the point from where the light appears to diverge after reflection or refraction is called image .
7) Define angle of incidence?
ans-the angle between the incident ray and the normal at the point of incidence is called angle of incidence.
8) Define angle of reflection?
ans-the angle between reflected ray and the normal at the point of incident is called angle of reflection.
9) what are the laws of reflection?
ans-(a)the incident ray, the reflected ray and the normal at the point of incident, all lie in the same plane.
(b) the angle of reflection and angle of incidence are equal.
10) define real and virtual image?
ans-if light after reflection converges to a point to form an image on its own it is called a real image.
if light after reflection diverging then it is to form a virtual image.
11) define erect and inverted image?
ans-if the image is upside down view of the given object then it is called inverted image .
if the image remains as the object is it is called erect image.
12) define plane mirror?
ans-a plane mirror always forms and erect virtual and size to size image at the same distance as the object is but at the back of the mirror.
13) define spherical mirror?
ans-are reflecting surface which is of the form of a square in which inner and outer surface is reflecting is called sperical mirror.
14) Define concave mirror?
ans-if the outer surface is silvered and the reflection takes place from inner surface of the mirror is called concave mirror.
15) define pole?
ans-the central point of the reflecting spherical surface is called pole.
16) define centre of curvature?
ans-the point about which the given spherical refracting surface can be made is centre of curvature.
17) define radius of curvature?
ans-the separation between the pole and the centre of curvature is called radius of curvature and the length of the radius of curvature is called focal length.
18) define principal axis?
ans-the straight line joining the pole and the centre of curvature is called principal axis.
19) define aperture?
Ans -the width of the reflecting surface is called aperture .
20) define focus?
Ans-the point on the principal axis where all the rays meet after reflection is called principal focus.
21) define focal length?
ans-the length of separation between the pole and the focus is called focal length.
22) where concave mirror can be used?
Ans-(a) as shaving mirror.
(b) as a reflector to concentrate light.
(c) as a reflecting type astronomical telescope.
(d) ine searchlight head on headlight of automobiles.
(e) in opthalmoscope to to examine throat and ear of a person generally parabolic mirrors are used.
23) where convex mirror can be used?
Ans-(a) as rear view mirrors in automobiles.
(b) as a device to check theft in shop.
(c) to bring view of corners which are not directly accessible.
24) what are the sign convention used to to determine the distance or measured?
ans-the set of rules to use'+'or''-'signs with the values while doing any problem problem in optics is called sign convention. they are :
(a)the object is placed on the left of the mirror so that the incident light moves left to right
(b) all measurement are to be made from the pole of the mirror.
(c)the distance measured in the direction of incident light will be taken as positive and the opposite direction will be taken as negative.
(d)all measurement of height above the principal axis are to be taken as positive and below are taken as negative.

10 P*01