Reflection Flashcards
What is the lase of reflection
Angle of incidence = angle of reflection
What is the difference between specular and diffuse/ irregular reflection
Specular/ regular reflection:
- reflected light leaves surface in a definite beam that follows the law of reflection
- Occurs on regular/ smooth surface
Diffuse/ Irregular reflection
- Incident light is reflected in all directions and does not follow the law of reflection
- occurs at irregular surfaces
What are the factors that affect reflection
Colour
Surface
Angle of incidence (in diffuse reflection only)
Refractive index
- the type of medium
How to calculate refractive index
Refractive index = velocity in vacuum (3 x10^8) / velocity in medium
What is fresnel’s law of reflection
% of light reflected = (n’-n/ n’+n) ^2 x 100
n= refractive index before refraction
n’= refractive index after refraction
What happens when light travels from a medium of lower to higher refractive index
Refracted ray bends towards normal, refracted angle is smaller thaan incident angle
what would happen if the ray entered at the normal
Incident and refracted angle = 0
How to find critical angle
critical angel = sin^-1 (n’/n)
What is the critical angle
Incident angle that yields refracted angle of 90 degrees
What is total internal reflection
When light travels from high to lower index interface and the incident angle is greater than the critical, rays are reflected back into same medium as incident ray
What is the aplication of total internal reflection at the cornea in optometric assesment
gonioscopy
What are the two spaces in a mirror
Real space
- real img a obj to left of mirror
Virtual space
- virtual obj n img to right of mirror
What is the most impt proptery of mirror?
n = -n’
What is the quality of a img formed by plane mirror
Virtual, erect, same size and shape as obj, image distance equal to object distance but opposite in sign
