Apparatus for the Study of

Photo Electric Effect

(Planck’s constant)

Model: HO-ED-EM-02

Holmarc's Photo Electric Apparatus (Model No: HO-ED-EM-02) is an instrument for studying the Photo Electric Effect and to obtain the Planck's constant.

A halogen source provides light energy to the photo tube. A filter wheel is placed in between the light source and photo tube to select different wavelengths. The filter wheel includes five narrow band interference filters to get the precise wavelength. A vacuum photo tube is kept inside the tube housing. This tube has very low anode dark current to achieve better results. The microprocessor controlled electronic interface gives the current and voltage readouts. The regulated power supply has 0 - 2V variable voltage to provide the stopping potential for electrodes. The ammeter gives accurate current output measurement facility. Toggle switch is provided to change the current range. The lamp house, filter wheel and photo tube housing are placed on an optical rail.

Experiment Examples

Determination of Planck's constant

If we plot the Stopping potential versus frequency will get a straight line whose slope is h/e , where h is the planck’s constant and e is the electron charge.

Stopping Potential v/s Frequency

Related Topics

Photoelectric effect

Work function

Absorption

Photon energy

Planck’s constant
Photo electric effect is the liberation of electrons from the surface of a material by absorption of energy from incident light. For each metal, there exists a minimum binding energy for electron, which is a characteristic of the element, called the work function .When a photon strikes a bound electron, it transfers its energy to the electron. If this energy is less than the metal's work function, the photon is remitted and no electrons are liberated. If this energy is greater than an electron's binding energy, the electron escapes from the metal with a kinetic energy equal to the difference between the photon's original energy and the electron's binding energy.
The stopping potential is measured by varying the anode voltage until the current drops to zero. The slope of a plot of stopping potential versus frequency is the value of the ratio, h/e. Hence the value of Planck's constant (h) and work function of the material can be determined. This instrument also imparts students, fundamental understanding of the quantum nature of light.
Features

The current amplifier is configured with high sensitivity and stability improve the accuracy of measurement

The optical filters are of high quality in order to reduce the error while selecting the wavelength

The photo tube has low levels of dark current and anode reverse current

Scope of Supply

Rail Based Platform

Model No: ED-EM-02-RP
Length
:
500 mm
Material
:
Anodized Aluminium Alloy
Quantity
:
1 no.

Filter Wheel with Interference Filters

Model No: ED-EM-02-FWIF
Diameter
:
25 mm
Wave length
:
404, 450, 505, 546, 578nm
Quantity
:
1no. each

Tungsten Halogen Lamp with Mount

Model No: ED-EM-02-THLM
Output Power
:
20 W
Quantity
:
1 no.

Photosensitive Device with Mount

Model No: ED-EM-02-PSD
Type
:
Vacuum photo tube
Quantity
:
1 no.

Photo Electric Effect Control Unit

Model No: ED-EM-02-PECU
Voltage
:
0 - 10 V
Current
:
nano - micro Amperes
Quantity
:
1 no.

Accessories

Dust protective Cover
User Manual

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