A convex lens of refractive index 1.5 has a focal length of 18 cm in air. Measure the change in its focal length when it is immersed in water of refractive index.
Distinguish among the terms 'average value' and 'rms value' of an alternating current.
The immediate current from an a.c. source is I = 5 sin (314 t) ampere. What are the average and rms values of the current?