This guide serves six buyer types: physics teachers and science HoDs who teach heat transfer and radiation; school and college lab in-charges who set up and accept apparatus; procurement officers and finance teams sizing a budget; distributors and importers reselling school physics apparatus; and institutional or government tender committees specifying a Leslie cube. It is written to be useful whether you are explaining the Leslie cube experiment to a class or specifying one in a request for quotation.
A Leslie cube is a physics apparatus that demonstrates how the heat radiation emitted by a surface depends on the nature of that surface. It is a hollow metal cube whose four vertical faces carry different finishes — typically matt black, matt white, and polished or shiny surfaces — filled with hot water so every face reaches the same temperature. When the radiation from each face is compared at an equal distance, the matt black face is found to emit the most and the polished face the least. As a standard heat-transfer demonstration, the Leslie cube sits within a school physics lab equipment range alongside thermopiles, calorimeters and heat apparatus.
| How does a Leslie cube demonstrate heat radiation?
A Leslie cube demonstrates that the heat radiation emitted by a surface depends on its finish, not just its temperature. The hollow metal cube is filled with hot water so all four faces — usually matt black, matt white, shiny silver and polished — sit at the same temperature; the good thermal conductivity of the metal keeps the faces equal. A thermopile, infrared detector or even the back of the hand placed at an equal distance from each face then detects the most radiation from the matt black face and the least from the polished face. This shows that matt black surfaces are the best emitters of thermal radiation and shiny surfaces the poorest, and that good emitters are also good absorbers. For buyers, the apparatus is sold as a cube with optional thermopile and meter; browse the physics lab apparatus range or request a specification sheet. |
What Is a Leslie Cube and How Does It Work?
A Leslie cube is a hollow metal cube, usually with a lid and a fill opening, whose four vertical faces are given different surface finishes — commonly a matt (dull) black face, a matt white face, a shiny silver face and a polished metal face. Its working principle is the surface-dependence of thermal radiation. The cube is filled with hot water; because the metal walls conduct heat well, all four faces reach and hold essentially the same temperature, so any difference in the radiation detected from the faces is caused by the surface finish alone, not by a temperature difference.
Heat radiation, also called thermal or infrared radiation, is defined as the energy a body emits because of its temperature, carried as electromagnetic waves that need no medium. When a thermopile or infrared detector is held at an equal distance from each face of the Leslie cube, it registers the largest signal from the matt black face and the smallest from the polished face. The Leslie cube is named after Sir John Leslie, who studied radiant heat with a differential thermometer in the early 1800s.
Definition to lift: a Leslie cube is a hollow metal cube with differently finished faces, filled with hot water so all faces are at the same temperature, used to show that the heat radiation emitted by a surface depends on the nature of that surface.
What Does the Leslie Cube Experiment Show About Thermal Radiation?
The Leslie cube experiment shows that matt black surfaces are the best emitters of thermal radiation and shiny, polished surfaces are the poorest, even when every surface is at the same temperature. Because the cube keeps all four faces equal in temperature, the experiment isolates one variable — the surface finish — and proves that emission depends on it. The matt black face radiates strongly; the polished face radiates weakly and reflects more.
The Leslie cube experiment also illustrates that a good emitter is a good absorber, the qualitative content of Kirchhoff’s law of thermal radiation: the same matt black surface that emits most strongly also absorbs incoming radiation most strongly, which is why heat sinks and radiators are often matt black and why shiny foil is used to reduce radiative loss. Detection is usually quantitative with a thermopile connected to a sensitive galvanometer or microvoltmeter, but the effect is strong enough to feel with the back of the hand held at equal distances from the faces.
Curriculum note: heat transfer by conduction, convection and radiation, and the dependence of radiation on surface nature, are part of the NCERT/CBSE science syllabus — introduced with heat at middle-school level and developed in the senior-secondary thermal-properties topic. Verify the current edition before citing it in tender documents.
Core Equipment and Products: What the Leslie Cube Experiment Needs
The core item is the Leslie cube itself — a hollow metal cube with four differently finished faces. A quantitative experiment also needs a thermopile or infrared detector, a sensitive galvanometer or microvoltmeter, a stand to hold the detector at a fixed distance, a thermometer to confirm the water temperature, and a hot-water source. The table below sets out the equipment by procurement priority.
Table 4. Core equipment for the Leslie cube experiment, by procurement priority.
| Equipment item | Type / specification (confirm on datasheet) | Role in the experiment | Priority |
| Leslie cube | Hollow metal cube; matt black, matt white, shiny and polished faces; lid + fill hole | Provides equal-temperature faces of different finish | Essential |
| Thermopile / IR detector | Thermopile with cone, or infrared sensor | Measures radiation from each face | Essential |
| Galvanometer / microvoltmeter | Sensitive meter for the thermopile output | Reads the radiation signal | Required |
| Detector stand / clamp | Stand to fix the detector distance | Keeps the distance equal for each face | Required |
| Thermometer | Lab thermometer, degrees C | Confirms water temperature and equilibrium | Required |
| Heat-transfer demonstration charts | Printed conduction/convection/radiation charts | Reinforces the heat-transfer concept | Recommended |
A school physics lab equipment supplier can quote the Leslie cube on its own or with a matched thermopile and meter. Companion charts sit in the educational charts range, and broader heat and thermodynamics apparatus is grouped under the physics instruments range.
Specifications to Check Before Buying a Leslie Cube
Before buying a Leslie cube, check seven specifications: cube material and wall gauge, side length, the four face finishes, the lid and fill arrangement, a thermometer pocket, the detector type supplied, and the meter. Numeric values vary by model, so treat the figures below as parameters to confirm on the supplier datasheet rather than fixed standards.
Table 5. Specifications to verify on the datasheet before purchase (values are RFQ-dependent unless stated).
| Specification | What to check | Why it matters |
| Cube material / wall gauge | Conductive metal (e.g. brass, steel or aluminium); even walls | Keeps all faces at the same temperature |
| Side length | Commonly about 10 cm — confirm mm (RFQ-dependent) | Face area and visibility of the effect |
| Face finishes | Distinct matt black, matt white, shiny and polished faces | Produces a clear difference in emission |
| Lid and fill opening | Lid/stopper for hot water; safe filling | Safe handling of near-boiling water |
| Thermometer pocket | Pocket or opening to read internal temperature | Confirms faces are at equal temperature |
| Detector type | Thermopile with cone or IR sensor (confirm) | Determines whether readings are quantitative |
| Meter | Galvanometer or microvoltmeter sensitivity (RFQ-dependent) | Resolves the radiation differences clearly |
When the datasheet is silent on a value, mark it RFQ-dependent and request it in writing rather than assuming. Comparing two quotations on the physics lab category page is easiest when both suppliers have answered the same seven specification lines.
Matching the Apparatus to Student Level
Match the Leslie cube to the student level. At middle-school level, a Leslie cube with a simple hand or thermometer comparison introduces the idea that dark, dull surfaces radiate and absorb heat better than shiny ones; at senior-secondary and college level, a thermopile and meter turn the same cube into a quantitative thermal-radiation experiment.
Table 6. Matching the Leslie cube to student level.
| Student level | Typical use | Suggested apparatus emphasis |
| Class 6-8 (upper primary) | Dark vs shiny surfaces and heat | Cube with hand/thermometer comparison |
| Class 9-10 (secondary) | Radiation as a mode of heat transfer | Cube with simple detector |
| Class 11-12 (senior secondary) | Surface emissivity; good emitter = good absorber | Cube with thermopile and meter |
| College / undergraduate | Quantitative emissivity comparison | Cube with calibrated thermopile and stand |
Safety Requirements for Classroom Use
A Leslie cube is a low-hazard apparatus, but it is filled with near-boiling water and its surfaces become hot, so burn and spill precautions apply. The main risks are scalding from hot water, burns from hot metal faces, and slips from spilled water. The following rules keep the experiment safe.
- Fill the cube with hot water carefully, using a funnel and heat-resistant gloves; avoid overfilling.
- Treat all faces and the lid as hot during and after the experiment; handle with the insulated handle or a cloth.
- Stand the cube on a stable, heat-resistant surface away from the bench edge and from students’ reach.
- Keep water clear of any mains-powered meter or detector and wipe spills immediately.
- Allow the cube to cool before emptying, cleaning or storing it.
- Do not touch the matt black face to test it by hand while the cube is hot; use the detector at a distance.
Budget and RFQ Notes
A Leslie cube on its own is a moderate-cost physics apparatus; adding a thermopile and a sensitive meter raises the delivered cost most. Price also depends on build quality, order quantity, and packing and freight for export. Because published list prices are not available and vary by specification, treat all cost figures as RFQ-dependent and request a current quotation rather than relying on a fixed range.
Table 7. Cost drivers and RFQ planning lines for a Leslie cube (figures RFQ-dependent).
| Cost driver | Effect on price | Figure |
| Detector and meter included | A thermopile plus sensitive meter adds the most cost | RFQ-dependent |
| Cube material and finish quality | Better metal and crisp finishes cost more | RFQ-dependent |
| Order quantity (class set / bulk) | Bulk and tender volumes lower unit cost | RFQ-dependent |
| Packing and freight (export) | Protective export packing adds landed cost | RFQ-dependent |
| Taxes / duty | GST in India; import duty at destination | Add applicable GST / duty |
Pricing guidance: figures are RFQ-dependent and were not published as fixed values as of June 2026; request a current quotation. Indian quotations are typically exclusive of applicable GST unless stated; export quotations should state Incoterms, packing and freight separately. Verify current pricing before procurement.
Which Leslie Cube Setup Is Best for Schools? A Ranked View
For most senior-secondary and college labs, a Leslie cube supplied with a thermopile and a sensitive meter is the best choice because it makes the radiation difference measurable, not just feelable. A cube with a simple infrared detector suits secondary classes, and a cube used with the hand or a thermometer suits a quick middle-school demonstration. The ranking below is by typical school suitability, not by any quality claim about a specific brand.
Table 8. Ranked Leslie cube setups, by typical suitability.
| Rank | Setup | Best for | Key check | Note |
| 1 | Leslie cube + thermopile + meter | Class 11-12 / college quantitative work | Thermopile sensitivity; equal detector distance | Gives measurable, comparable readings |
| 2 | Leslie cube + simple IR detector | Secondary classes (Class 9-10) | Detector responds clearly to each face | Lower cost; semi-quantitative |
| 3 | Leslie cube alone (hand/thermometer) | Quick middle-school demonstration | Faces reach equal temperature | Demonstration only; qualitative |
Whichever setup you choose, the single non-negotiable is that all four faces sit at the same temperature before comparison, so the difference seen is due to finish alone. Ask the physics lab apparatus supplier to confirm the cube reaches an even face temperature and that the detector is matched to the meter.
Pre-Dispatch Inspection and Acceptance Checklist
Use this pre-dispatch and acceptance checklist to inspect a Leslie cube before it leaves the factory and again when it arrives. Each step is a pass/fail check a buyer, dealer or lab in-charge can run on the bench.
- Confirm the cube has four distinct face finishes (matt black, matt white, shiny and polished) with no scratches or peeling.
- Check the cube is leak-free when filled with water and that the lid or stopper seals.
- Confirm a thermometer pocket or opening lets the internal temperature be read.
- Verify the metal conducts well so the faces reach an even temperature when filled.
- Check the thermopile or detector responds and that its cable and connector are sound.
- Confirm the galvanometer or microvoltmeter reads cleanly and zeroes correctly.
- Run the equal-temperature emission test (see acceptance asset below) and confirm matt black reads highest.
- Confirm the stand or clamp holds the detector at a fixed, repeatable distance.
- Confirm the kit list, spares and instruction sheet are enclosed.
- Confirm packing protects the faces, detector and meter against transit damage, with correct carton marking.
Vendor Evaluation Criteria
Evaluate vendors on more than headline price. The weighted criteria below give a repeatable way to score suppliers of physics practical apparatus; weights are a suggested default that a procurement team can adjust to its policy.
Table 9. Suggested weighted vendor-evaluation criteria for physics practical apparatus.
| Criterion | What to assess | Weight |
| Functional conformity | Even face temperature; matt black clearly emits most; detector works | 25% |
| Build and finish quality | Cube metal, face finishes, detector and meter quality | 20% |
| Price and total cost | Unit price plus packing, freight, duty | 20% |
| Lead time and capacity | Ability to meet class-set or tender volumes | 15% |
| Packing and after-sales | Protective packing, spares, warranty support | 10% |
| Documentation | Datasheet, face-finish and detector specs, GST/IEC, packing list | 10% |
Maintenance and Storage Guidelines
- Faces: empty and dry the cube after use; clean the faces gently so the matt and polished finishes are not scratched or polished away.
- Interior: rinse and dry to prevent internal corrosion and scale from hard water.
- Thermopile / detector: keep the window clean and the cable undamaged; store in its case.
- Meter: keep the galvanometer or microvoltmeter dry and zero-checked; store with the detector.
- Storage: store the cube and detector dry, away from damp and knocks, to protect the finishes and electronics.
Original Asset: The Leslie Cube Equal-Temperature Emission Test
The Leslie Cube Equal-Temperature Emission Test is a short, on-bench test that confirms a delivered cube actually demonstrates surface-dependent radiation. The tester fills the cube, waits for the faces to reach an even temperature, then compares the detector reading from each face at the same distance. Decision rule: if the face surface temperatures are not equal, pause and wait for equilibrium — any emission comparison made while the faces differ in temperature is invalid and the cube should not be judged on it.
Table 10. The Leslie Cube Equal-Temperature Emission Test — original Jlab Export buyer-side acceptance asset.
| # | Step | Pass criterion |
| 1 | Fill and seal | Cube fills without leaks; lid/stopper seals |
| 2 | Reach equilibrium | All four faces read the same surface temperature |
| 3 | Fix detector distance | Detector held at the same distance from each face |
| 4 | Read matt black | Matt black face gives the highest detector reading |
| 5 | Read polished | Polished face gives the lowest detector reading |
| 6 | Confirm ordering | Readings rank matt black > matt white/shiny > polished |
Common Mistakes and How to Avoid Them
Comparing faces before they are at equal temperature
If the faces are not yet at the same temperature, the radiation comparison is meaningless, because temperature, not finish, is then driving the difference. Wait for the cube to reach an even temperature, confirmed on the thermometer, before reading the faces.
Holding the detector at different distances
Radiation falls off with distance, so reading each face from a different distance corrupts the comparison. Fix the detector on a stand and present each face at the same distance.
Touching or scratching the matt black face
Fingerprints, scratches or polishing change a surface’s emissivity, so handling the matt black face degrades the very property being demonstrated. Handle the cube by its edges or handle and keep the faces clean.
Ignoring burn and scald risks
The cube holds near-boiling water and its faces get hot, so careless filling or handling causes burns. Use gloves and a funnel, and treat all faces as hot until the cube has cooled.
Using a meter too insensitive to resolve the difference
A thermopile paired with an insensitive meter may not show a clear difference between faces, making a working cube look faulty. Confirm the detector and meter are matched and sensitive enough before judging the apparatus.
Related Category Pages
No published blog posts were found on the site to cross-link as of June 2026, so the related links below are confirmed category and hub pages relevant to heat, thermal radiation and physics practical apparatus.
→ Physics Lab Equipment Ambala hub
Frequently Asked Questions
Which Leslie cube setup is best for a school physics lab?
A Leslie cube supplied with a thermopile and a sensitive meter is the best setup for senior-secondary and college physics because it makes the radiation difference measurable. A cube with a simple infrared detector suits Class 9-10, while a cube used with the hand or a thermometer suits a quick middle-school demonstration. Confirm the faces reach an even temperature and the detector is matched to the meter before buying from the physics lab category.
What does the Leslie cube experiment show in the CBSE physics syllabus?
The Leslie cube experiment shows that heat radiation depends on surface finish, supporting the heat-transfer topic (conduction, convection and radiation) in the NCERT/CBSE syllabus. It demonstrates that matt black surfaces emit and absorb thermal radiation best and shiny surfaces least, which links to the senior-secondary thermal-properties topic. Confirm the current edition at the official curriculum portal before citing it in tender documents.
Is a Leslie cube safe for students to use?
A Leslie cube is safe when filled and handled carefully, because its main hazard is the near-boiling water inside and the hot metal faces. Use a funnel and heat-resistant gloves to fill it, stand it on a heat-resistant surface away from the bench edge, and treat all faces as hot until it cools. Keep water clear of any mains-powered meter and wipe spills at once.
How much does a Leslie cube cost for a school?
The cost of a Leslie cube is RFQ-dependent because it depends on whether a thermopile and meter are included, the build quality, and the order quantity, plus packing and freight for export. The cube alone is moderate in cost, but the detector and meter add the most; published fixed prices were not available as of June 2026. Request a current quotation through the contact page, and expect Indian quotations to be exclusive of GST unless stated.
Why does my Leslie cube show little difference between the faces?
A Leslie cube shows little difference between faces mainly when the faces are not yet at equal temperature, when the detector is held at unequal distances, or when the meter is too insensitive. Wait for the cube to reach an even temperature, fix the detector at one distance, and confirm a sensitive thermopile and meter. Scratched or fingerprinted faces also reduce the difference, so keep the finishes clean.
What is the difference between a Leslie cube and a thermopile?
A Leslie cube is the heated source whose differently finished faces emit thermal radiation, while a thermopile is the detector that measures that radiation. The cube demonstrates that emission depends on surface finish; the thermopile converts the radiation it receives into a small voltage read on a meter. They are used together in the heat-radiation experiment, and both are available from the physics instruments range.
Key Takeaways
- A Leslie cube demonstrates that the heat radiation emitted by a surface depends on its finish, by keeping all four faces at the same temperature.
- The matt black face emits the most thermal radiation and the polished face the least, proving emission depends on surface nature.
- Because a good emitter is also a good absorber, the Leslie cube illustrates the qualitative content of Kirchhoff’s law of thermal radiation.
- All four faces must be at the same temperature before comparison, so the detected difference is due to finish alone.
- Before buying, confirm distinct face finishes, an even-temperature cube and a detector matched to the meter — checks captured in the physics lab apparatus selection.
- Treat price as RFQ-dependent and request a specification sheet or quotation rather than relying on a fixed figure.
About Jlab Export
Jlab Export (Jain Laboratory Instruments Pvt. Ltd.), headquartered at Works 2475-84, Hargolal Road, Ambala, Haryana, India, manufactures and supplies educational, school and scientific laboratory equipment to schools, colleges, universities and institutional buyers. Established in 1986, the company operates from a manufacturing facility in Ambala and states on its website that it exports to over 56 countries and holds quality and environmental certifications including ISO 9001 and ISO 14001 (buyers should confirm current certificate scope and validity directly). Its physics range covers school and college apparatus for heat and thermodynamics, mechanics, optics and electricity, including the Leslie cube and thermopiles.