66) When freely suspended, the compass needle come to rest along the geographic

A) north-east directions
B) east-west directions
C) south-east directions
D) north-south directions

67) If x and y are the temperatures of the hot and cold water samples respectively and z is the final temperature of their mixture, then

A) y>x>z
B) x>y>z
C) x>z>y
D) y>z>x

68) If i and r are the angle of incidence and angle of refraction, then the equation for the Snell’s law is

A) sini+sinr = constant
B) sini-sinr=constant
C) sinixsinr=constant sini
D) = constant sin t

69) A lens is made up of

A) a transparent material
B) an opaque material
C) both transparent and opaque materials
D) none of these

70) The distance between the focal point and the optic centre gives the

A) radius of curvature
B) focal length
C) object distance
D) image height