a. Convex and concave lens.
|It is thick in the middle and thin at the edges.||It is thin in the middle and thick at the edges.|
|It converges the parallel beam of light.||It diverges the parallel beam of light.|
|It has a real focus.||It has a virtual focus.|
|It has +ve power.||It has -ve power.|
b. Virtual image and real image.
|It cannot be cast on the screen.||I can be cast on the screen.|
|It is always erect.||It is always inverted.|
|It is formed by the apparent intersection of rays at a point.||It is formed by the actual intersection of rays at a point.|
c. Myopia and hypermetropia.
|It is the defect of vision in which a person can see nearby objects but cannot see distant objects.||It is the defect of vision in which a person can see distant objects but cannot see nearby objects.|
|It is also called short-sightedness.||It is also called long-sightedness.|
|It is corrected by using a concave lens.||It is corrected by using a convex lens.|
d. Far point and near point.
|Far point||Near point|
|The distant point from the eye which can be seen clearly is called the far point.||The nearest point which an eye can see the object clearly is called the near point.|
|The far point is at infinity for a normal eye.||The near point is at 25 cm for a normal eye.|