Google Books

https://books.google.co.uk/books?id=MCyU91APOP0C&pg=PA10&lpg=PA10&dq=chemical+reaction+of+light+on+a+film+camera&source=bl&ots=gJdp-OuNH3&sig=v48u-jJ539tRY0zYvG_hx_CGkfA&hl=en&sa=X&ved=0ahUKEwi65YqijsrSAhVJGsAKHQktB-8Q6AEIPzAG#v=onepage&q=chemical%20reaction%20of%20light%20on%20a%20film%20camera&f=false

Book: Chemical Reactions by Denise Walker

Info: This book is a chemistry education book therefore has nothing to do directly with film, however it does briefly mention in a very small paragraph about the chemical reaction taking places on film for photography.

How do Digital Cameras Work?

http://www.explainthatstuff.com/digitalcameras.html

This website mostly goes through detail on how digital cameras work and how they use digital camera technology, but it introduces the topic of discussion with how film cameras work too. Therefore gives a bit of depth to both parts of the essay, but also goes into a bit more detail on the digital side.