Optics

Reflection

1. The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
2. The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.
3. The reflected ray and the incident ray are on the opposite sides of the normal.

Refraction

1. Occurs when light passes through a different medium 
2. Angle between incident ray and normal as compared to emergent ray and normal is the same
3. Refractive Index = sin i / sin r OR 1 / sin c
4. Critical Angle = sin^-1 (1/Refractive Index) 

*i=Angle between incident ray and normal; r=Angle between refracted ray and normal; c= Critical angle

Lenses

These are the 6 different positions for lenses which will produce different types of images, like whether it is real or virtual, inverted or upright and magnified, diminished or the same as before.