# Notes on Ray Optics Homework Problems

Received a few questions about the homework, a few of them are challenging.  If the language of the book doesn’t make sense, ask me questions.  Generally I can decipher what they mean.  Problem #54 is probably the most complicated problem, you need to use a bit of trigonometry.  Draw a large diagram for that problem and it should be a little easier.

For #41, basically you need a more than one triangle and a few variables.  It uses geometry and algebra both.  As well as the law of reflection.  You might want to draw out the rays and then use parallel and perpendicular lines to create other triangles that might be useful.

51, the key phrase in the problem is that when you look at the target, the gaze is 30 degrees below horizontal.  I’ll draw a diagram of what that means tomorrow in class.

54, it’s asking for the angle labeled in the diagram theta 1 for ‘total internal reflection on the hypotenuse of the glass prism’.  So specifically against the edge that is the hypotenuse of the triangular prism.

60, there is a piece of glass on top of an amoeba, the thickness is given.  The light will refract when it enters the glass making it appear like the amoeba is in a different position.  It’s similar to the example I did in class with the air bubble in the middle of the submarine window.  You use a derived equation – equation 18.7.

71, use the magnification equation and thin lens equation.  It will be a converging lens since the image is real.  And it says the image will be smaller and upright (it doesn’t specifically say upright, but apparently it’s implied).