Final answer:
The 60-W bulb in Figure 6-1a will be brighter than the 25-W bulb. The brightness of the bulbs in Figure 6-1c cannot be determined without additional information.
Step-by-step explanation:
The brightness of a bulb is determined by its power rating. Therefore, the 60-W bulb in Figure 6-1a will be brighter than the 25-W bulb. The higher the power rating, the more electrical energy is converted into heat and light, resulting in a brighter bulb.
In Figure 6-1c, the brightness of the bulbs cannot be determined without additional information. We would need to know the power ratings of the bulbs to predict their brightness accurately.