Question

1a) Explain why the solid-liquid phase boundary of water is so steep

1b)Consider the P-V isotherms of the van Waals equation. Why are the isotherms for temperatures less than the critical temperature unphysical?

1c) Describe what happens to the interference pattern produced by a diffraction grating as you increase the spacing between slits.

Answer 1

Question 1A

The solid liquid phase boundary for water is steep becuase ice is less dense then water, and a higher pressure will favour start to favour water.

Question 1B

The isotherms below the critical temperature are unphysical as they fail to predict behaviour of gases when they are in equilibrium with a liquid, i.e during a first-order transition.

Question 1C

The width of fringes in a diffraction pattern is given by

Increasing the spacing between the slits, i.e , the sine term has to get smaller, as the term on the right, is constant.

Since the sine term is smaller, the angle also becomes smaller. Hence, the central fringe, as well as the other fringes, become narrower.