Figure 3-41 Objects at Different Temperatures Have Different Colors and Brightnesses This sequence of photographs shows the changing appearance of a piece of iron as it is heated. As the temperature increases, the amount of energy radiated by the bar increases, and so it appears brighter. The apparent color of the bar also changes because, as the temperature increases, the peak wavelength of light emitted by the bar decreases. The labeled stars shown have roughly the same temperatures as the bars above them.