Explain how fluorescent tubes work
Fluorescent tubes are filled with low pressure mercury, when an electric current is passed through, the electrons in mercury are excited and move to a high energy level, this high level state is unstable and so the electron moves back to its original state, but on doing so, it emits an electromagnetic wave with energy equivalent the difference in energy level. This is UV light and the electrons in the phosphor coating inside the fluorescent tube are excited, and releases visible light when the electrons return to its orginal energy state, which provides the glow in fluorescent lights.
MW
Related Physics A Level answers
All answers ▸A water jet starts at a point X and reaches its maximum height at a point Y. Air resistance has a negligible effect on the motion of the water jet. (i) State the direction of the force acting on the jet at Y. (1 mark)
Using Newton's law of universal gravitation, show that T^2 is proportional to r^3 (where T is the orbital period of a planet around a star, and r is the distance between them).
A 4 metre long bar rotates freely around a central pivot. 3 forces act upon it: 7N down, 2m to the left of the pivot; 8N up, 1m to the left of the pivot; 4N up, 1m to the right of the pivot. Apply one additional force to place the bar in equilibrium.
Two electrons are a distance r apart, the first electron exerts a force F on the second electron. a) What force does the second electron exert on the first? b) In terms of r, at what distance is the force that the first electron exerts on the second F/9?