Most of people believe that reading in dim light can damage eyesight. In fact, not likely, even if you reading too much in any light can. But we can not deny that reading in dim light can make you in high risks of decreasing eyesight. So, you'd better listen to your father's advices to keep eye health. Good luck.
Not exactly, but what you should know is that the light is a an important factor to be considered whenever we are using our eyes, no matter reading, watching TV, using computer or even in our habitable room. Dazzling bright light should definitely be avoided. It's too strong a stimulation to the eyes and will soon lead to eye fatigue. On the contrary there may be no enough light be reflected into our eyes in dim light, and we need to try to see figures clearly, which also increases the burden of eyes. Ideally, the light is mild. If you are reading under an energy saving bulb, the surrounding shouldn't be dark also, which is too distinct a contrast. There is a particular kind of eye-protection lamp, especially good for children-using, which is characterized with a high frequency provided by variable frequency electronic ballast, with the power of 30w~40w, frequency of 6000Hz~8000Hz.