Question

the time period of ocillations pendulumis 2 seconds. what is it fequency

Answer 1

Time period = 2 sec

in 2 seconds the pendulum makes 1 oscillation
in 1 second the pendulum will make 1/2 = 0.5 oscillation.

we know 
frequency is the number of oscillations made in 1 sec

therefore 
frequency = 0.5 hz