QUANTUM EFFECTS
7A10.26 PHOTOELECTRIC EFFECT7A10.33 PHOTON ENERGY AND FREQUENCY
7A10.40 SOLAR POWERED CART
7A50.40 METAL RING VIBRATIONS
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7A10.26 Photoelectric Effect Demonstrate photoelectric effect using phototube. Light shining on phototube produces voltage proportional to intensity. You can show that color of light makes a difference by putting red & blue filters next to tube but 7A10.33 is better to show E(photon) = hf.
Setup Requirements: Ask ahead of time. Phototube must be connected to op amp circuit to drive display meter. Circuit assembled as needed. A voltmeter is used. The current is way too low to measure with demonstration equipment.
Equations: None Safety Issues: Handle tube carefully. It cannot be replaced. |
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7A10.33 Photon Energy and Frequency The dependence of photon energy on frequency can be demonstrated by slowly raising the voltage. The LEDs will come on in order of increasing frequency of the color of the light produced (red/orange, yellow/green, dark green, blue). Setup Requirements: Assembled as needed. Start with power supply voltage on zero. Slowly increase using fine voltage knob. Red will glow around 1.6v. Maximum voltage is 2.6v. Connect positive lead to resistors and negative lead to LEDs.. Equations: E = hf. Energy is proportional to applied voltage. Safety Issues: Burning out LED. Maximum voltage is 2.6v. |
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7A10.40 Solar Powered Cart Demonstrate photoelectric effect using solar cell. Bright light shining on solar cell will run motor to move cart. Setup Requirements: Minimal. Use a large flashlight to move across floor or desk. Ask at least 1 working day ahead of time. The bright flashlights may need recharging. Equations: E = hn Safety Issues: Don't let cart run off table. If enough space do on floor. |
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7A50.40 Metal Ring Vibrations Demonstrate standing waves in metal ring. Three, five and seven anti-nodes can be produced. Use as model of electron orbit in early quantum theory or as model for string theory.
Setup Requirements: Assembled as needed. Drive with function generator. Adjust until resonance occurs. Start around 20 Hz. Even numbers can be obtained by holding ring at top. Equations: Circumference of ring equal to odd number of half wavelengths Safety Issues: None |
