When the temperature of an ideal gas is increased from 27$$^\circ$$C to 127$$^\circ$$C. Calculate the percentage increase in its $$v_{rms}$$.

Two waves are represented by $$x_1=A \sin \left(\omega t+\frac{\pi}{6}\right) \text { and } x_2=A \cos \omega t \text {. }$$ Then, the phase difference between them is

Assertion (A) The focal length of lens does not change when red light is replaced by blue light.

Reason (R) The focal length of lens does not depend on colour of light used.

The wavefront is a surface in which