Chapter 1
Refraction of Light 1. Reflection always occurs when a ray hits any surface such that: a. The incident [SI] ray and the reflected ray [IR) lie on the same side with respect to the surface. b. The incident ray [SI] and the reflected ray [IR) lie on opposite sides with respect to the Normal (NI). c. The angle of incidence (i) is always equal to the angle of reflection (r).
R
R

N
N
Reflected ray
Reflected ray

Normal (Perpendicular to the surface at the point of incidence I)
Normal (Perpendicular to the surface at the point of incidence I) i i r r
S
S
I
I
Surface
Surface
Incident ray
Incident ray
Source of light
Source of light

2. Refraction occurs when light traverses from one transparent medium into another transparent medium hence the surface separating the two media should also be transparent. d. When refraction occurs: i. The incident ray [SI] and the refracted ray [IS’) lie on opposite sides with respect to the surface. ii. The incident ray [SI] and the refracted ray [IS’) lie on opposite sides with respect to the Normal (NI). iii. The angle of incidence (i) is either greater or smaller than the angle of refraction (i’) except when the incident ray is perpendicular to the surface where i = i’.
Normal (Perpendicular to the surface at the point of incidence I)
Normal (Perpendicular to the surface at the point of incidence I) Transparent Medium 1: Where the incident ray is issued and where reflection occurs
Transparent Medium 1: Where the incident ray is issued and where reflection occurs
R
R

N
N

i i r r S
S
Incident ray
Incident ray
Source of light
Source of light

Reflected ray
Reflected ray

Transparent Surface
Transparent Surface

S2’
S2’
i2’ i2’ I
I

Case 2: Refracted ray with i2’ > i ray deviates away