The power of a concave lens of focal length 20 cm is ____________
50 D
0.05
-5 D
5D
On reducing the focal length of a lens its power
Doesnot change
Nothing can ve said
Decreases
Increases
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
The centre of the sphere whose part is the lens surface, is called the ____________ of that surface of the lens.
None of these
Centre of curvature
Radius of curvature
Principal foci
A ray of light after refraction through a lens emerges parallel to the principal axis of the lens. The incident ray either passes through or apper to meet
Second focus
Centre of curvature of first surface
Optical centre
First focus
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 con cavo-convex 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
Thin at the centre with one surface plane
Which lens is converging?
Concave lens
convex lens
Both (a) and (b)
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
A convexo - concave lens is
