26.A closed organ pipe has a frequency n. If its length is doubled and radius is halved, its frequency nearly becomes

27.The intensity of sound wave gets reduced by 20% on passing through a slab. The reduction in intensity on passage through two consecutive slabs is

28.Starting from the origin a body oscillates simple harmonically with a period of 2 s. After what time will its kinetic energy by 75% of the total energy?

29.A spring of force constant k is cut into two pieces such that one piece is double the length of the other. Then the longer piece will have a force constant of: