56) The materials which are useful in making of diodes, transistors and integrated chips (ICs) etc. are

A) conductors
B) insulators
C) semiconductors
D) alloys

57) The defect of vision in which the people cannot see the objects beyond far point is called

A) presbyopia
B) hypermetropia
C) myopia
D) the angle of vision

58) For a healthy eye, the accommodation of eye lens will be in the range of

A) 2 to 2.5 cm
B) 2.5 to 25 cm
C) 1 to 2 cm
D) 2.5 to 2.27 cm

59) A person cannot see the objects placed between near point of least distance of distinct vision. His defect of vision can be corrected by using

A) bi-concave lens
B) bi-convex lens
C) bi-focal lens
D) concavo-convex lens

60) Dioptre is the unit of

A) Refractive index
B) Focal length
C) Radius of curvature
D) power of the lens