Lenses

Question 1

Converging lense

Answer 1

Lens is thickest in the meddle and thinner at ends

Question 2

Optical center

Answer 2

O

Centre of the lens (perpendicular to principle axis)

Question 3

Diverging lense

Answer 3

Lens is thicker at ends and thinner in middle

Refracted rays must be extended back

Question 4

Where are the Principal and secondary focus located on a diagram

Answer 4

Principle focus (F) 
Same side of the lens relative to incident rays 

Secondary focus (F’)
Opposite side of the lens relative to the incident rays

Question 5

Rules for converging lenses

Answer 5

1. An incident ray that is parallel to the P. A. will refract through F
2. An incident ray that goes through O will go right through with no refraction
3. An incident ray through F’ refracts parallel to the P. A.

Question 6

Rules for diverging lenses

Answer 6

1. An incident ray that is parallel to the P. A. will refract as if originated from the F
2. An incident ray that is directed at F’ will refract parallel to the P. A.
3. An incident ray that goes through O will go right through with no refraction