Finding a clear point of research

After re-reading my initial proposal and the feedback, I've decided that my area of research is still too open. I really don't know where to start researching first, so I've made some bullet points to help narrow it down.

• I am interested in how each wave of feminism differ from each other
• What kind of lasting impact has feminism had?

For now, I want to stick to these two points for my research. When I discuss each 'wave' in my essay, I want to use at least one example of feminist illustration from that era and discuss what kind of impact this might have had on the cause.  To do this I need to define more clearly when I think each 'wave' began/ended. 

In terms of essay structure, so far I am thinking:

1. Introduction. What is feminism? When did it begin? How successful has it been so far? What is a 'wave' of feminism?
2. First wave feminism. When did it begin and who started it? Why did it begin? How successful was it? Did all women agree with it?
3. Second wave feminism. When did it begin? Was there an event that triggered a new wave of protests? How successful was it? How did it differ from the first wave? Did all women agree with it? Was it a generation thing?
4. Third wave feminism. When did it begin? Was there an event that triggered it? Have advances in technology aided the cause? How does it differ from previous waves? Is it actually affecting any change? 
5. Conclusion. Overall, how has each wave of feminism changed? - goals, active participants etc. How effective has it been thus far? - Compare women's rights now to those of 150 years ago. Is it still relevant and still affecting change?