Wilhelm Rontgen showed that when electrons strike a material in the cathode ray tube, some rays are originated that can cause fluorescence in the fluorescent material placed outside the cathode ray tubes. He named these rays as X-rays as these were not deflected by electric and magnetic field. X-rays are used as a diagnostic tool in the treatment of disease and bone fracture. An intelligence officer, John catched a smuggler by using this X-ray machine. He was trying to smuggle the drugs while travelling abroad.
The approximate wavelength of X-rays is ............

What do you mean by hydrogen economy? How can it be helpful for our society?

Ionic compounds have high melting and boiling points. There is strong electrostatic force of attraction between them. Answer the following:
(i) Why ionic solids are poor conductor of electricity?
(ii) What happens to the electrical conductivity when they are dissolved in water?
(iii) What is the value associated with it?

(i) What do you mean by diffusion?
(ii) Ammonia and hydrochloric acid gases are prepared at the two extreme corners in the laboratory. Which gas will reach first to a person in the centre of the laboratory?
(iii) Write down the value points

While working in laboratory a student kept ferrous sulphate in a vessel made up of zinc. After few days he found cracks in the container.
(i) Why cracks were found in the container?
(ii) Write down the chemical reaction takes place.
(iii) What is the value associated with this?