Light

Question 1

Define ‘reflection’

Answer 1

The rebounding of light at a surface.

Question 2

Define ‘incident ray’ of reflection

Answer 2

Light ray that hits the reflecting surface.

Question 3

Define ‘reflected ray’ of reflection

Answer 3

Light ray that bounces off the reflecting surface

Question 4

Define ‘angle of incidence’ of reflection

Answer 4

The angle between the incident ray and the normal.

Question 5

Define ‘angle of reflection’

Answer 5

The angle between the reflected ray and the normal.

Question 6

Define ‘normal’

Answer 6

The perpendicular to the reflecting surface at the point of incidence.

Question 7

State the relationship between ‘i’ and ‘r’ for reflection

Answer 7

The ‘i’ is equal to the ‘r’.

Question 8

Define ‘refracted ray’

Answer 8

The light ray that enters a medium and undergoes a change of direction.

Question 9

Define ‘incident ray’ of refraction

Answer 9

The light ray that striked a surface.

Question 10

Define ‘angle of incidence’ of refraction

Answer 10

The angle between an incident ray and the normal at the point of incidence.

Question 11

Define ‘angle of refraction’

Answer 11

The angle between a refracted ray and the normal at the point of incidence.

Question 12

Define ‘optical medium’

Answer 12

A material through which light can pass through.

Question 13

Define ‘interface’

Answer 13

The surface separating 2 phases of matter.

Question 14

What is the speed of vacuum?

Answer 14

3x10^8 m/s

Question 15

What is the relationship between sin i and sin r?

Answer 15

n ( refractive index ) = sin i / sin r

Question 16

What is the refractive index of an optical medium?

Answer 16

The ratio of the speed of light in vacuum to the speed of light in the medium.
n = c / v

Question 17

How does light bend as it travels from one optical medium to another?

Answer 17

Bend towards normal when it enters an optically denser medium.

Bend away from normal when it enters an optically less dense medium.

Question 18

Define ‘critical angle’

Answer 18

The angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90 degree.

Question 19

Define ‘total internal reflection’

Answer 19

The complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium.

Question 20

Conditions required to undergo total internal reflection.

Answer 20

1. Light ray in an optically denser medium strike its boundary with an optically less dense medium.
2. Angle of incidence is greater than the critical angle of the of the optically denser medium.

Question 21

Formula for critical angle

Answer 21

sin c = 1 /n

Question 22

Define ‘focal length’

Answer 22

The distance between the optical centre C and the focal point F.

Question 23

Define ‘focal plane’

Answer 23

The plane that passes through the focal point F and perpendicular to the principal axis.

Question 24

Define ‘optical centre’

Answer 24

Midpoint between surfaces of the lens on its principal axis.

Question 25

Define ‘focal point’

Answer 25

The point at which all rays parallel to the principal axis converge after refraction by the lens.

Question 26

What are convergeing lens and diverging lens?

Answer 26

Converging lens causes light rays to converge to a point. Thicker in centre.

Diverging lens causes light rays to diverge from a point Thinner in centre.

Question 27

What is the relationship between object distance and the type of image?

Answer 27

When u > f, image formed is real, inverted and on opposite side of the lens as the object.

When u ≤ f, image formed is virtual, upright and on same side of the lens as the object.