chapter 14 - light

Question 1

2nd law of reflection

Answer 1

angle of incidence is equal to the angle of reflection

Question 2

1st law of reflection

Answer 2

incident ray, reflected ray and normal at the point of incidence lie on the same plane

Question 3

refraction

Answer 3

bending of light as it passes through from one optical medium to another

Question 4

1st law of refraction

Answer 4

incident ray, reflected ray and normal at the point of incidence lie on the same plane

Question 5

refractive index (of a medium)

Answer 5

ratio of the speed of light in a vacuum to the speed of light in that medium

Question 5

2nd law of refraction

Answer 5

for two given media, the ratio of the sine of angle of incidence to the ratio of the sine of angle of refraction is constant

Question 6

principle of reversibility of light

Answer 6

regardless of how many times a light ray has been reflected or refracted, it will follow the same path when its direction has been reversed

Question 7

total internal reflection

Answer 7

complete reflection of a light ray in an optically denser medium at the boundary with an optically less dense medium

Question 7

critical angle

Answer 7

the angle of incidence is an optically denser medium for which the angle of refraction is the less dense medium is exactly 90

Question 8

principal axis

Answer 8

the line which passes through the centre of the lens and is perpendicular to the plane of the lens

Question 9

optical centre C

Answer 9

the point on the principal axis that is the midpoint between the surfaces of the lens

Question 10

principal focal point F

Answer 10

the point on the principal axis where all the rays parallel to the principal axis meet after passing through the lens

Question 11

focal plane

Answer 11

the plane perpendicular to the principal axis on which all parallel rays meet after passing through the lens

Question 12

focal length L

Answer 12

the distance between the optical centre C and the principal focus point F

Question 13

real vs virtual image

Answer 13

real image can be formed on a screen placed at the image plane but a virtual image cannot be formed on a screen placed at its image plane

Question 14

extent of refraction of light from one medium to another

Answer 14

• from optically denser to optically less dense, bends towards normal (speed of light decreased)
• from optically denser to optically less dense, bends away from normal (speed of light in medium increased)