A ray of light incident at a point on the principal axis of a convex lens, passes un deviated through the lens. What special name is given to this point on the principal axis?
Optical centre
First focal point
Second focal point
None of these
A ray of light directed towards the optical centre of a lens, after refraction:
is reflected black
Passes through the focus
Be comes paralll to the principal axis after refraction
Passes undeviated
The centre of the sphere whose part is the lens surface, is called the ____________ of that surface of the lens.
Centre of curvature
Radius of curvature
Principal foci
Which lens is diverging?
Convex lens
Both (a) and (b)
Concave lens
The power of a concave lens of focal length 20 cm is ____________
50 D
0.05
-5 D
5D
Which lens is converging?
convex lens
Which is diverging lens?
All of these
Concavo convex lens
equi-convex lens
Equi concave lens
The power of a lens is +2.0 D. Find its focal length and state what kind of lens it is
5 cm, convex
50 cm, convex
5 cm, concave
50 cm, concave
A convexo - concave lens is
Thick at the centre and thin at the periphery
Thin at the centre and thick at the periphery
Thick at the centre with one surface plane
The relationship between the power of a lens and its focal length is ___________
Focal length + power = 0
Power = 1/focal length
Power = 2focal length
Power = focal length / 2