Time period of a simple pendulum is measured at karachi, what change will occur in the time period ,if it is measured on mount everest

Anybody wanna ? (picture included? )

Hydrogen and helium are both members of?

Light traveling in water, nwater = 1.33, strikes a plastic block at an angle of incidence of 51.4°; part of the beam is reflected and part is refracted. if the index of refraction of the plastic is 2.0, what is the angle made by the reflected and refracted beams?