One of the following readings represents the measurement of the length of a metal rod using vernier callipers. Taking the reading accuracy into consideration, the most likely one is 

When a sound wave passes from air into water its 

A convex mirror is used as a driving mirror because 

I. its image is erect     

II. It has a large field of view

III. It has a long focal length 

Identify the CORRECT statement(s) 

Two mirrors of the same length are arranges as show in the diagram. A ray of light NO strikes the system at O and emerges along PQ. The emergent ray has been deviated through 

A magnetic needle is suspended first at the earth's north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are