Refractive index and colour of a light

 Red colour has longest wavelength so it has maximum speed in a medium compared to other colours.  As it travels with maximum speed in a medium,  the refractive index of the medium for Red colour is minimum.

MECHANICAL ADVANTAGE , VELOCITY RATIO

Which is always constant for a machine of given design: MA or VR ?

Ans: VR remains constant for a machine of given design as it depends on the distances moved by the load and effort but MA can vary due to the friction developed between the moving parts of the machine.

LENZ'S LAW

LENZ'S LAW is based on law of conservation of

a) mass

b) charge

c) momentum 

d) energy.

Ans: d)   energy