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We offer a complete experiment for the study of Planck's Constant and verification of inverse square law of radiation using a photocell.
1. Determination of Planck's Constant and Work Function of Materials by Photoelectric Effect
It was observed as early as 1905 that most metals under influence of radiation, emit electrons. This phenomenon was termed as photoelectric emission.
The experimental facts provided the strong evidence that the electromagnetic field is quantified and the field consists of quanta of energy E= hn where n is the frequency of the radiation and h is the Planck's constant. These quanta are called photons.
2. To verify inverse square law of radiation using a photoelectric cell
THE APPARATUS ConSIST OF THE FOLLOWING:-
(1) Photo Sensitive Device: Vacuum photo tube.
(2) Light source: Halogen tungsten lamp 12V/35W
(3) Colour Filters: 635nm, 570nm, 540nm, 500nm & 460nm
(4) Accelerating Voltage: Regulated Voltage Power Supply
- Output: ± 15V continuously variable through multi-turn pot
- Display: 3 ½ digit 7-segment LED
- Accuracy: ± 0.2%
(5) Current Detecting Unit: Digital Nanoammeter
It is high stability low current measuring instrument
- Range: 1000 μA, 100 μA, 10 μA & 1 μA with 100% over ranging facility
- Resolution: 1 nA at 1 μA range
- Display: 3½ digit 7-segment LED
- Accuracy: ± 0.2%
(6) Power Requirement: 220V ±10%, 50Hz or 110V ±10%, 60Hz. as required
(7) Optical Bench: The light source can be moved along it to adjust distance between the light source and the phototube, scale length is 400mm. A tube is provided to install colour filter and a focus lens is fixed in the back end.
The circuit is all electronic using transformer and electronic components Viz. IC’s, transistors, capacitors and resistance etc. The whole circuit operates on 200V ± 10% 50 Hz AC and mounted in a metallic cabinet which is grounded through the grounding lead of power connector and hence safe towards electrical hazard, if any.
The set-up is complete in all respect, no additional accessory is required.
Planck's Constant Experiment
