(a) A vertical plane passing through the axis of a freely suspended magnet is
       called the magnetic meridian
   (b) A vertical plane passing through the axis of rotation of the Earth is called
       the geographical meridian
   (c) The degree to which the magnetic field can penetrate a medium is known
       as the relative permeability of the medium
   (d) The relative permeability is not a dimensionless quantity
Ans: (c)
106. If an object is placed at the centre of curvature of a concave mirror, the
   position of the image is [NDA 2010]
   (a) at the principal focus
   (b) between the principal focus and the centre of curvature
   (c) at the centre of curvature
   (d) beyond the centre of curvature
Ans: (b)
107. The radius of curvature of a plane mirror [NDA 2010]
   (a) is zero
   (b) is infinity
   (c) can be anywhere between zero and infinity
   (d) none of the above
Ans: (b)
108. The rainbow appears due to : [RRB CC 2005]
   (a) reflection
   (b) refraction
   (c) scattering
   (d) both reflection and refraction
Ans: (d)
109. The sky appears blue: [RRB 2004]
   (a) due to dispersion
   (b) due to refraction
   (c) due to scattering
   (d) due to reflection