61) If ‘R’ is radius of curvature of mirror and Y is focal length, which of the following relation is correct?
A) R = f
B) 2R = f
C) R + 2f = 0
D) R – 2f = 0
62) Parallel rays incident on a concave mirror, on reflection meet at what point?
A) At pole
B) At focal point
C) At centre of curvature
D) Any where
63) Type of mirror used by dentists is
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) None
64) A spherical mirror whose reflecting surface curved outwards is
A) Convex mirror
B) Concave mirror
C) Plane mirror
D) All the above
65) In case of Bi-concave lens line joining centre of curvatures is of what shape ?
A) Straight line
B) Curved outside
C) Curved inside
D) None
66) In case of lenses, light rays travelling through principal axis
A) Travel in same line without deviation
B) Always converge at one point
C) Always diverge at-one point
D) Converge (or) diverge depending upon type of lens
67) Which one of the following material can be used to make lens?
A) Iron
B) Plastic
C) Glass
D) Clay
68) Which of the following is true in case of concave lens?
A) Erect and virtual image
B) Inverted and real image
C) Erect and real image
D) Inverted and virtual image
69) Which of the following indicates lens formula ?
A) f =
B) 1/f =
C) 1/f = v-u
D) f =
B) 1/f =
70) Focal plane of a lens is a plane
A) Parallel to principal axis at the focus only
B) Perpendicular to principal axis at the focus
C) Parallel to principal axis at centre of curvature
D) Perpendicular to principal axis at centre of curvature
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