Mass cannot be converted into energy.(True/ False)

The e.m. waves of radio frequency cannot be reflected by ionosphere. (True/False)

The e.m. waves of radio frequency cannot be reflected by ionosphere. (True/False)

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false Assertion: In a nuclear process mass gets converted into energy. Reason: According to Einstein's mass energy equivalence relation, mass m is equivalent to energy E, given be the relation E=mc^2 where c is the speed of light in vacuum.

The energy required to knock an electron completely out of an atom is called excitation energy. (true/false)

The behaviour of conductors, semiconductors and insulators can be explained on the basis of energy bands.(True/False)