Taking out paste frome a tooth paste tube is an expmple to highlight which physical property?

What type of defect can arise when a solid is heated ? Which physical property is affected by it and in what way ?

On moving diagonally across the periodic table, the second and third period elements show certain similarities .Pick out the which shows such a property.

We brush our teeth with tooth paste because it is ………… in nature.

The wavelength of K_alpha X-ray of tungsten is 21*3 pm. It takes 11*3 keV to knock out an electron from the L shell of a tungsten atom. What should be the minimum accelerating voltage across an X-ray tube having tungsten target which allows production of K_alpha X-ray?