IB DP Physics: HL复习笔记4.4.2 Reflection

• When light hits a smooth plane surface, most of it gets reflected
• Very smooth reflective surfaces (e.g. mirrors) are known as specular plane reflectors
• For these surfaces, the law of reflection applies:

The angle of reflection is equal to the angle of incidence 

i = r

• Where:
  • The angle of incidence (i) is the angle between the incident ray and the normal
  • The angle of reflection (r) is the angle between the reflected ray and the normal

A light ray being reflected by a mirror

• The wavelength of the reflected ray is the same as that of the incident ray

a) State the angle of reflection

Step 1: Recall the definition of the angle of incidence (i)

• • The angle of incidence is the angle between the incident ray and the normal
  • This is not the 30° angle marked in the diagram

i = 90° – 30°

i = 60°

Step 2: Recall the law of reflection  

The angle of reflection is equal to the angle of incidence

Step 3: State the angle of reflection (r)

r = 60°

b)  Add the incident and reflected wavefronts to the diagram

Step 1: Recall that wavefronts and rays are perpendicular to each other

• • Add at least three equally spaced wavefronts all perpendicular to the incident ray
  • Add at least three equally spaced wavefronts all perpendicular to the reflected ray