High School Labs Equipments Lab Equipment Manufacturer, Supplier and Exporter in India

Advanced Physics Lab Experiments

Three requirements before any of this apparatus works

These experiments measure small quantities, and every one of them is defeated by the same three things. A department that buys the apparatus without addressing them will conclude the apparatus is faulty.

• A clean mains supply. Several of these experiments resolve currents in the nanoampere range or voltages of a few millivolts, and mains-borne noise swamps them. If your supply is noisy - and in many places it is - specify or arrange a line conditioner or regulated supply for the bench. This is the commonest reason advanced physics apparatus is believed to be defective.
• A vibration-free bench. The Millikan experiment in particular is defeated by a bench that moves when someone walks past. A heavy, independent bench away from doors and corridors is part of the installation.
• Control of light. The photoelectric and oil-drop experiments need a dim room, and stray light enters as a background current or as an inability to see the drops. Blinds, and a bench that is not under a window.

Tell us about all three when you enquire. We would rather discuss the room than quote apparatus into a room that will defeat it.

Planck's constant, two ways, and why both are in the listing

The listing has the photoelectric method and the light-emitting diode method, and they are not duplicates - they are a cheap route and a rigorous route to the same constant.

• The photoelectric method is the historically and physically rigorous experiment: measure the stopping potential at several known frequencies, plot it against frequency, and the slope is Planck's constant divided by the electronic charge. What it needs to work: a decent set of narrow-band filters or a stable monochromatic source, a sensitive current measurement, and a dim room. The filters are the item most often skimped on, and a filter set with wide passbands blurs the very frequencies the plot depends on.
• The light-emitting diode method determines the constant from the threshold voltage at which diodes of several colours begin to emit. It is far cheaper, needs no filters and no dark room, and it is excellent teaching - a student sees the relationship between photon energy and colour directly. Its honest limitation is that the threshold voltage is not exactly the photon energy, so the value obtained is approximate; the experiment teaches the physics and should not be presented as a precision determination.

Our advice for a laboratory buying one: the LED method for a first course, the photoelectric method where the syllabus requires a determination of the constant. A department with both gets the better of both - the cheap experiment introduces the idea, the rigorous one tests it.

Franck-Hertz: the temperature is the experiment

This is the most frequently reported "not working" experiment in an advanced physics laboratory, and the cause is almost always the same. The apparatus measures a current through a vapour as the accelerating voltage rises, and the characteristic peaks appear only within a narrow window of vapour pressure - which is set by the oven temperature.

• Too cold and there are too few atoms for the electrons to excite: the current rises smoothly with no structure.
• Too hot and the electrons collide so often that they never reach the excitation energy: the current is suppressed and again featureless.
• In the window, the peaks and troughs appear and their spacing is the excitation energy - the result the experiment exists for.

So when specifying: ask about the oven and its temperature control and stability, not only about the tube. A controlled, stable, readable oven is what makes the experiment reproducible between groups, and a crude heater makes it a matter of luck. Ask also for the recommended operating temperature range in writing, and have the first group establish the working point and record it for everyone else.

The ionization potential set-up in this listing works on closely related principles and has the same requirements: a stable supply, a sensitive current measurement, and patience with the operating point.

Millikan oil drop: the hardest result in the undergraduate laboratory, usefully

We would rather set the expectation honestly. Getting a good value for the electronic charge from an oil drop apparatus is genuinely difficult - it requires a vibration-free bench, good illumination, a steady hand on the atomiser, patience in selecting a drop that falls slowly enough to time, and a willingness to repeat the measurement many times and treat the scatter properly.

That difficulty is the pedagogical value, and it is worth saying to the class in advance: this is the experiment in which students meet real experimental scatter and have to decide what to do about it, which is a skill no neat experiment teaches. The apparatus is not faulty because the first drop gives a poor answer.

Practical points for the order: ask what oil is specified and whether it is supplied - the viscosity enters the calculation, so substituting an arbitrary oil invalidates the result; treat the atomiser and the oil as consumables; and check the illumination and the viewing optics, because a drop that cannot be seen clearly cannot be timed.

Charge-to-mass ratio: remember the earth

The e/m apparatus uses a magnetic field, usually from Helmholtz coils, to bend an electron beam into a circle whose radius gives the charge-to-mass ratio. There is one systematic error that catches almost every class and is trivial to remove: the earth's magnetic field adds to the applied field.

At the field strengths used in a teaching apparatus this is not negligible, and it produces a result that is consistently off rather than scattered - which is the hardest kind of error for a student to spot. The remedy is to orient the apparatus so that the applied field is perpendicular to the local horizontal component of the earth's field, or to reverse the coil current and average the two results, which cancels it. Either way it is worth teaching deliberately, because "a consistent offset means a systematic error, not bad luck" is one of the most useful lessons in experimental physics.

Four-probe and electron spin resonance: solid state measurements

The four-probe method measures the resistivity of a semiconductor by passing current through two probes and measuring voltage across two others, which removes the contact resistance that defeats a two-probe measurement. The point to teach, and the one most often left out of a student's report: the raw reading must be multiplied by a geometry correction factor that depends on the sample thickness and the probe spacing. A resistivity quoted without that correction is simply wrong, and the correction is not small.

With an oven, the same apparatus gives resistivity against temperature and hence the band gap, which is the more interesting experiment - so ask whether the oven and its controller are included, and what temperature range they cover.

Electron spin resonance detects the resonance of unpaired electron spins in a magnetic field, and two specifications decide whether the experiment is any good: the uniformity of the magnetic field over the sample volume, which sets the narrowest line the apparatus can resolve, and its stability, since a drifting field smears the resonance. Ask about both, and ask what sample is supplied - the standard teaching sample is a stable free radical, and without it the apparatus has nothing to resonate.

For the magnetic field measurement apparatus that accompanies these experiments, the question is how the probe is calibrated and whether a calibration certificate or a reference magnet is supplied; a field meter of unknown calibration turns every one of the above into a relative measurement.

What to tell us when you enquire

• The level and the syllabus - these are undergraduate and postgraduate experiments, and the specification differs between a teaching set and a research-grade set.
• Your mains supply quality, and whether a regulated supply or line conditioner is available on the bench.
• Bench type and location: vibration, daylight, and distance from doors and corridors.
• For Franck-Hertz: the oven control and stability required.
• For four-probe: whether the oven and controller are needed, and the temperature range.
• For electron spin resonance: field uniformity and stability, and whether a sample is supplied.
• Which consumables and accessories must be included - filters, oil, atomiser, samples, reference magnet.
• Supply voltage and frequency, and destination country.

Related ranges: science teaching equipment for school-level science, geography lab models, metallurgical equipment for materials work, and industrial training kits. The full educational kit and educational lab equipment categories list the rest.

Frequently asked questions

Are these really high school experiments?

No, and we would rather say so than let a school order them. Planck's constant, Franck-Hertz, Millikan, four-probe resistivity and electron spin resonance are final-year undergraduate and postgraduate experiments. The category name is wrong and we have flagged it for correction. If you are equipping a school, the science teaching equipment range is the right place to start; if you are equipping an advanced physics laboratory, this is the right range and the environmental requirements above matter as much as the apparatus.

Our Franck-Hertz apparatus shows no peaks. Is it faulty?

Check the oven temperature first - that is the cause in most cases. Too cold and there are too few atoms to excite, so the current rises smoothly; too hot and the electrons collide before reaching the excitation energy, so the current is suppressed. The peaks appear only in a window of vapour pressure. Establish the working temperature with one group, record it, and give it to the rest - and when specifying, ask about oven control and stability rather than only about the tube.

Which Planck's constant experiment should we buy?

The light-emitting diode method for a first course - cheap, no filters, no dark room, and it shows the relationship between photon energy and colour directly, with the honest caveat that the value obtained is approximate. The photoelectric method where the syllabus requires an actual determination; there, do not skimp on the filters, because a wide passband blurs the frequencies the whole plot depends on.

Why are our Millikan results so scattered?

Because that is what the experiment is like, and it is the point. It needs a vibration-free bench, good illumination, careful drop selection, many repeats and a proper treatment of the spread - and it is where students first meet real experimental scatter and have to decide what to do about it. Check the bench and the lighting, confirm you are using the specified oil since its viscosity enters the calculation, and set the expectation with the class in advance.

Why is our e/m value consistently off?

Almost certainly the earth's magnetic field adding to the applied field, which produces a consistent offset rather than scatter. Orient the apparatus so the applied field is perpendicular to the local horizontal component of the earth's field, or reverse the coil current and average the two results. It is worth teaching deliberately: a consistent offset indicates a systematic error, which is a different diagnosis from a noisy one.

What is the commonest reason advanced physics apparatus appears not to work?

Mains noise. Several of these experiments resolve nanoamperes or millivolts, and electrical noise on the supply swamps the signal - so the apparatus looks defective when the room is the problem. Before concluding anything is faulty, try the experiment on a regulated or conditioned supply. Vibration and stray light are the next two causes, in that order.

Key takeaways

• This is an advanced physics range, not a school one. The category name is wrong and is being corrected.
• Clean mains, a still bench and control of light decide whether any of this apparatus performs. Address the room with the order.
• Franck-Hertz lives or dies by the oven. Specify temperature control and stability, and record the working point.
• Do not skimp on photoelectric filters; and treat the LED method as excellent teaching rather than a precision determination.
• Four-probe readings need the geometry correction factor - a resistivity quoted without it is wrong.
• A consistent e/m offset is the earth's field. Orient the apparatus, or reverse the current and average.

About this page

Ray Export is a manufacturer and exporter of laboratory, scientific and educational equipment based at Plot No. 449, HSIIDC Industrial Area, Saha, Ambala, Haryana 133104, India. Enquiries: [email protected], +91-9817319615.

Written by Palak Mall, Senior Content Writer. Technically reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory and testing instrumentation. Last updated: 17 October 2026.

Notes on this listing, published rather than hidden: the category name describes a school range and the contents are advanced undergraduate and postgraduate physics - flagged for renaming. One record in the middle of the sequence carries the prefix GLM- instead of HSLE- (the Millikan oil drop apparatus), which is a geography-lab prefix, and that code is already in use by a different product in our geography listing - so the same code now identifies two different products. It is flagged as a database fix. Product names carry the padding phrase "For Physics Lab For High School", which has truncated several of them, and apostrophes have been stripped ("Planck s Constant"); we print the correct forms here because they are what a specifier searches for. Oven ranges, filter sets, field uniformity figures, supplied consumables and all other specifications will be confirmed in writing on the quotation. Verify them before tender submission.