A pendulum clock is lifted to a height where the gravitational acceleration has a certain value of g. Another pendulum clock of same length, but of double the mass of the bob is lifted to another height where the gravitational acceleration is $${g \over 2}$$. The time period of the second pendulum would be (in terms of period T of the first pendulum)

The loudness of sound depends upon the

Two bodies of mass M each are placed R distance apart. In another system, two bodies of mass 2M each are placed $${R \over 2}$$ distance apart. If F be the gravitational force between the bodies in the first system, then the gravitational force between the bodies in the second system will be

Light rays move in straight lines. But through an optical fibre, they can move in any type of zig-zag path because