There is nothing illegal if you are using it for your college classroom presentation ....not for monetizing it. Even in Google every photo has not copyright. Many photos posted there are too copied from somewhere else. It is not legal If You Are using any copyright content/images from Google publicly. Using for college course may not be considered as profiting, public use or broadcasting.
If the photograph, or the website it is in, does not have a copyright notice attached, then it is probably OK to use it for non-commercial purposes, such as what you intend to do. However, I would suggest giving a mention during your presentation that the photos were not your own creation, that they were borrowed from the Internet. This will show your interviewers that you are humble, honest and will give credit to the proper source and, above all, that you will not plagiarize your future colleagues. This is a huge issue with the academic community. Good luck with the job interview.
You must state where the photos came from. Just the same as if you copied information straight from an encyclopedia. If your work becomes public later on you will need to give credit where credit is due.
