Light-Reflection and Refraction

Question 1

Laws of Reflection of Light?

Answer 1

1) The angle of incidence is equal to the angel of reflection.
2)The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane.
These laws are applicable to all types of surfaces, including spherical mirrors.

Question 2

One of the best reflectors of Light?

Answer 2

Silver Metal is one of the best reflectors of Light.

Question 3

Properties of image formed by plane mirror?

Answer 3

1) Virtual and Erect
2) Size of the image is equal to the size of the object.
3) The image formed is as far behind the mirror as the object is in front of it.
4) The image is laterally inverted.

Question 4

Spherical mirrors?

Answer 4

Mirrors whose reflecting surfaces are spherical are called spherical mirrors. It is the most commonly used type of curve mirror.

Question 5

Real Images?

Answer 5

Formed when rays of light actually meet.
Can be obtained on screen. Example- cinema screen.
Can be formed by concave mirrors.

Question 6

Virtual Images ?

Answer 6

Formed when light rays only appear to meet( but do not meet actually).
Virtual images cannot be obtained on screen.
Example- Our image in a mirror.
Can be formed by plane mirrors.

Question 7

Converging mirror?

Answer 7

Concave mirror.

Question 8

Diverging mirror?

Answer 8

Convex mirror.

Question 9

Principal focus of a concave mirror?

Answer 9

Point on the principal axis where all the rays parallel to the principal axis converge after reflection.

Question 10

Principal focus of a convex mirror?

Answer 10

Point on the principal axis where all the reflected rays appear to converge after reflection.

Question 11

Principal Focus is represented by what?

Answer 11

Principal focus is represented by the letter F………..

Question 12

Position of an object for Concave Mirror

At Infinity

Answer 12

At Focus
Highly diminished, point sized
Real and inverted.

Question 13

Position of an object for a Concave Mirror’

Beyond C

Answer 13

Between F and C
Diminished
Real and inverted.

Question 14

Position of an object for a Concave Mirror

At C

Answer 14

At C
Same size
Real and inverted.

Question 15

Position of an object for a Concave Mirror

Between C and F

Answer 15

Beyond C
Enlarged
Real and inverted.

Question 16

Position of an object for a Concave Mirror

At F

Answer 16

At Infinity
Highly enlarged
Real and inverted.

Question 17

Position of the object for a Concave Mirror

Between P and F

Answer 17

Behind the mirror
Enlarged
Virtual and erect.

Question 18

Rule 1) for Concave and Convex mirrors

Answer 18

A ray parallel to the principal axis, after reflection, will pass through the principal focus in case of a concave mirror or appear to diverge in case of a convex mirror.

Question 19

Rule 2) For Concave and Convex mirrors

Answer 19

A ray passing through the principle axis of a concave mirror or a ray which is directed towards the principal focus of a convex, after reflection, will emerge parallel to the principal axis.

Question 20

Rule 3) For Concave and Convex mirrors

Answer 20

A ray passing through the centre of curvature of a concave mirror or directed in the direction of the center of curvature of a convex mirror, after reflection , is reflected back along the same path. The light rays come back along the same path because the incident rays fall on the mirror along he normal to the reflecting surface.

Question 21

Rule 4) For Concave and Convex mirrors

Answer 21

A ray incident obliquely to the principal axis, towards ta point P (Pole of the mirror)o the concave mirror or a convex mirror is reflected obliquely. The incident and the reflected rays follow the laws of reflection at the point of incidence ( Point P), making equal angles with the principal axis.

Question 22

Object Position for Convex Mirror

At Infinity

Answer 22

At the Focus F, behind the mirror
Highly diminished, point sized
Virtual and Erect

Question 23

Object Position for Convex Mirror

Between Infinity and the pole P of the mirror

Answer 23

Between P and F, behind the mirror
Diminished
Virtual and Erect

Question 24

New Cartesian Sign Convention

Answer 24

i) The object is always placed to the left of the mirror. This implies that the light from the object falls on the mirror from the left-hand side.
ii) All distances are parallel to the principal axis are measured from the pole of the mirror.
iii) All the distances measured to the right of the origin are taken as positive while those measured from the left of the origin are taken as negative.
iv) Distances measured perpendicular to and above the principal axis are taken as positive.
v) Distances measured perpendicular to and below the principal axis are taken as negative.

Question 25

Refraction of Light?

Answer 25

Light does not travel in the same direction in all media. It appears that when travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomena is known as refraction of light.

Question 26

Laws of Refraction of Light

Answer 26

i) The incident ray, the reflected ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.
ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour and for the given pair of media. This law is also known as the Snell’s Law of refraction.

Question 27

Lens

Answer 27

A transparent material bound by two surfaces, of which one or both surfaces are spherical, forma a lens. A lens may have two spherical surfaces, bulging outwards. It is called a double convex lens or it is simply called a convex lens. It is thicker in the middle as compared to the edges. Convex lens is also called converging lens.
A double concave lens is bounded by two spherical surfaces, curved inwards. It is thicker at the edges than at the middle. It is a diverging lens.