911. A lens which converges a beam of parallel rays to a point is called
A. Diverging (or concave) lens
B. Converging (or convex) lens
C. Plano concave lens
D. Plano-convex lens

912. A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called
A. Center of curvature
B. Focus
C. Optical centre
D. Aperture

913. The diameter of a lens is called
A. Focal length
B. Principal axis
C. Aperture
D. Radius of curvature

914. In going form a denser to rarer medium a ray of light is
A. Deviated
B. Bent away from the normal
C. Bent towards the normal
D. Polarized

915. Unit of the power of a lens is
A. Meter
B. Watt
C. Dioptre
D. Horsepower

916. Dioptre power of a concave lens of 10 cm focal length is
A. 10 dioptre
B. 10 dioptre
C. 1 / 10 dioptre
D. 1 / 10 dioptre

917. The power of a concave lens is
A. Real
B. Virtual
C. Positive
D. Negative

918. The minimum distance between an object and its real image in a convex lens is
A. 2 f
B. 2.5 f
C. 3f
D. 4f

919. If an object is placed away from 2f of a converging lens then the image will be
A. Real and erect
B. Virtual and erect
C. Real and inverted
D. Virtual

920. A convex lens gives a virtual image only when the objects lies
A. Between principal focus and centre of curvature
B. Beyond 2 f
C. At the principal focus
D. Between the principal focus and an optical center