The calorific value is highest for: MCQ with Answer and Explanation

Explanation:
Cathode rays are streams of fast-moving electrons, not electromagnetic waves, originating from the cathode in a discharge tube. Because they are material particles traveling in straight lines, they can be stopped by opaque objects, thus casting sharp shadows. Therefore, statements 1 and 3 are correct.

Explanation:
Rusting is a chemical change because iron reacts with oxygen and moisture to form a completely new chemical substance, hydrated iron(III) oxide (Fe₂O₃·xH₂O), which has different chemical properties from iron and cannot be easily reversed by simple physical means like heating or cooling.

Explanation:
John Dalton formulated the law of multiple proportions: If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers. Lavoisier gave law of conservation of mass. Proust gave law of definite proportions. Dalton's atomic theory explained these laws.