Question

An electron and a positron travel at 2.0 × 104 m/s toward a region of finite magnetic field (isolated within the lines) directed into the page as shown. A positron is identical to an electron (mass, etc) except that it has a positive charge. Immediately before they enter the field they are 1.0 mm apart.

(a) What is the magnitude of the electrostatic force between them right before they enter the magnetic field?

(b) The electron and positron enter the region with the magnetic field where they both travel in a straight line staying 1.0 mm apart as they traverse the field. What is the strength of the magnetic field?

(c) If the position of the electron and the positron were flipped, so that the electron was on the top and the positron on the bottom, could they still travel straight through the field? Explain.

4. (12 pts) A tank whose bottom is a mirror is filled with water to a depth of 20.2 cm. A small fish floats motionless 7.40 cm under the surface of the water. Use the following index of refraction: water = 1.33 and air = 1.00.

(a) What is the apparent depth of the reflection of the fish in the bottom of the tank when viewed from directly above?

(b) When looking into the tank, at what angle θ with respect to the normal (in the water) will you no longer be able to see the fish through the top surface of the tank?

(c) What happens to the light rays from the fish with angles larger than θ with respect to the normal?

Answer 1