Light-Reflection

Question 1

define light

Answer 1

light is form of energy which is a part of the electromagnetic spectrum. It posesses rectilinear propgation and does not requre any medium for its propogation

Question 2

define reflection

Answer 2

reflection is the process of bouncing back of light into the same medium after striking a surface.

Question 3

state the two laws of reflection

Answer 3

• the incident ray, reflected ray and normal to the reflecting surface all lie on the same plane.
• the angle of incidence is always equal to the angle of reflection.

Question 4

what are the two types of images and define them

Answer 4

real image
-if the rays of light from an image after reflection actually meet a point then a real image is formed

virtual image
-when a beam of light from an object, after rflectiin, does not actually meet at a point but seems to diverge from it, then the image is a virtual image.

Question 5

differenciate between real and virtual image

Answer 5

real image

• formed when light rays actually meet at a point after reflection
• image is always inverted
• image is formed in front of a mirror
• it can be obtained on a screen
  ex: concave mirror

virtual image

• light rays do not meet at a point after reflection but appear to diverge from it
• image is erect
• image cannot be obtained on a screem
• image is formed behind a miror
  ex: plane mirror,convex miroor

Question 6

characteristics of image formed by a plane mirror

Answer 6

• image formed is virtual and erect
• size of the image is equal to the size of the object
• the distance between the object and the mirror is equal to the distance between the image and the mirror
• the image formed is laterally inverted

Question 7

define spherical mirror

Answer 7

a mirror whose reflecting surface is curved or a part of a hollow sphere is called a sphericla mirror

Question 8

define concave mirror

Answer 8

a spehrical mirror whose reflecting surface is curved inward is called a concave mirror

Question 9

define convex mirror

Answer 9

a spherical mirror whose reflecting surface is bulged outward is called a convex mirror

Question 10

what is the pole of the mirror

Answer 10

the centre of the reflecting surface of a spherical mirror is caled the pole of the mirror
denoted by :P

Question 11

what is the centre of curvature

Answer 11

centre of curvature is the centre of the hollow sphere of which the spherical mirror forms a part of.
denoted by:C

Question 12

what is radius of curvature

Answer 12

radius of curvature is the radius of the hollow sphere of which the spehrical mirror forms a part of,
denoted by: R

Question 13

define principal axis

Answer 13

principal axis is the imaginary line passing throuhg the cetnre of curvature and pole of the mrror

Question 14

define focus of a concave mirror

Answer 14

rays parallel ot principal axis after refletion converge at a point on the principal axis caled the focus of a concave mirror
denited by:F

Question 15

focallenght

Answer 15

distance between P and F

R=2f

Question 16

rules for image formation on concave mirror

Answer 16

i) a ray parallel to the principal axis, after reflection, passes through the focus
ii) a ray which passes through the focusafter reflection moves parallel to the principal axis
iii) a ray which passes through the centre of curvature after relfection retraces its path.
iv) a ray which is incident at the pole obliquely gets reflected obliquely making the same angle.

Question 17

rules for image formation on convex mirror

Answer 17

i) a ray which is paralllel to the principal axis after reflection diverges and appears to come from the focus
ii) a ray directed towards the focus after reflection moves parallel to the principal axis
iii) a ray directed towards the centre of curvature retraces its path
iv) a ray which is incident at the pole obliquely gets reflected back obliquely making the smae angle

Question 18

define regular reflection

Answer 18

when parallel rays of light strike a smooth and highly polished surface then the relfected rays of light are also parallel and are directed towards the same direction.This is known as regular reflection

Question 19

define irregular reflection

Answer 19

when parallel rays of light strike a rough surface with irregularities, the reflected light is not parallel but spreads over a large area. This is known as irregular reflection.

Question 20

define normal

Answer 20

the perpendicular to the reflecting surface at the point of incidence

Question 21

define incident ray

Answer 21

the ray of light which striked the reflecting surface

Question 22

define relfected ray

Answer 22

they ray of light which is bouncing back/ reflected form the relfecting surface at the point of incidence.

Question 23

what is the focus and radius of curvature of a plane mirror

Answer 23

focus: ∞

radius of curvature=0

Question 24

define linear magnification

Answer 24

linear magnification is the ratio of the height of the image to the height of the object.
m=hᵢ/hₒ

Question 25

define mirror formula

Answer 25

mirror formula is the equation which gives the relationsip between focal length, image distance and object distance.

1/v+1/u=1/f

Question 26

define ray

Answer 26

a ray of light is the path followed by light energy in a transparent medium

Question 27

define beam

Answer 27

a group of parallel rays of light emitted by a source of light is called beam