When a metal is heated its density decreases. There are two sources that give rise to this diminishment of ρ: (1) the thermal expansion of the solid, and (2) the formation of vacancies (Section 5.2). Consider a specimen of gold at room temperature (20?C) that has a density of 19.320 g/cm3. (a) Determine its density upon heating to 800?C when only thermal expansion is considered.

When a metal is heated its density decreases. There are two sources that give rise to this diminishment of ρ: (1) the thermal expansion of the solid, and (2) the formation of vacancies (Section 5.2). Consider a specimen of gold at room temperature (20?C) that has a density of 19.320 g/cm3.
(a) Determine its density upon heating to 800?C when only thermal expansion is considered.
(b) Repeat the calculation when the introduction of vacancies is taken into account. Assume that the energy of vacancy formation is 0.98 eV/atom, and that the volume coefficient of thermal expansion, αv is equal to 3αl.
thin film of oil (no = 1.50)with varying thickness floats on water (nw = 1.33)When it is illuminated from above by white light, the reflected colors are as shown in Fig. 24–60. In air, the wavelength of yellow light is 580 nm. (a) Why are there no reflected colors at point A? (b) What is the oil’s thickness t at point B?