Select the most appropriate antonym of the given

In which type of wave do the particles of the medium vibrate perpendicular to the direction of wave propagation?  

The half-life of a radioactive substance is 5 hours. How much of the substance remains after 15 hours?       

Going from fluorine to chlorine, to bromine and then to iodine, the electro negativity:

What is the escape velocity from the surface of the Earth?

Why does a fountain pen leak on an airplane flying at high altitude?

What type of radiation is produced by a hot object emitting energy?  

Which of the following gas is used in the manufacture of Vanaspati Ghee? 

What does Ohm's Law state?  

Which of the following is a characteristic of a conductor?  

The resistance of a wire is directly proportional to: