Laser Optics Experiment Tank Kit

Quick Answer: The Laser Optics Experiment Tank Kit is a transparent tank used with a laser beam so students can see light travelling through water and watch reflection, refraction and total internal reflection happen. It belongs with the optics experiment kits for schools that turn ray diagrams into something visible.

Making the Beam Visible

A laser beam in clean air or clear water is almost invisible from the side, because nothing scatters its light towards the viewer. The laser optics experiment tank solves that: the water is made faintly cloudy with a few drops of milk or a pinch of fluorescent dye, and the beam appears as a bright line. Chalk dust or a fine water mist above the surface shows the beam in the air as well, so students can watch the ray bend where it crosses the water surface.

With the beam visible, the core experiments follow. Aim the beam down into the water at an angle and measure how it bends towards the normal (refraction). Aim it up from below the surface and increase the angle until the beam no longer leaves the water but reflects back inside: total internal reflection, the principle of optical fibres. A small mirror placed in the tank adds reflection under water.

The critical angle for water is about 49 degrees, and students can measure it and compare it with the value calculated from the refractive index of water, about 1.33. The laser type and power class, the tank size and any accessories supplied with this kit should be confirmed, and the school’s laser safety rules applied.

Specifications

Care & Handling

• Never look into the laser or point it at anyone; keep the beam below eye level and stop it with a card on the far side of the tank.
• Remove watches and rings, and keep shiny tools out of the beam path to avoid stray reflections.
• Mop up spills straight away and keep the laser and any mains-powered equipment away from the water.
• Empty, rinse and dry the tank after use so no film or algae forms on the walls.

Experiments

• Measuring angles of incidence and refraction to calculate the refractive index of water
• Finding the critical angle and demonstrating total internal reflection
• Modelling an optical fibre with a beam trapped by repeated reflection
• Showing why a straw looks bent in a glass of water

Why Choose LabEquip

Physics departments buy the tank kit because it lets a whole class watch refraction and total internal reflection instead of reading about them. LabEquip lists it in the STEM kits range, and it complements the apparatus in the light and optics section. Ask about quantities on the contact page.

Frequently Asked Questions

Why add milk or dye to the water?

Tiny particles in faintly cloudy water scatter some of the laser light sideways, so the beam becomes visible from the side. Too much makes the water opaque, so add a few drops at a time.

How do students show total internal reflection?

Direct the beam upward from inside the water towards the surface and increase its angle from the normal. Beyond the critical angle, about 49 degrees for water, the beam reflects back into the water instead of leaving it.

What kind of laser is used for school experiments?

Schools normally use low-power visible lasers, typically class 2, under their laser safety rules. Confirm the class of any laser supplied with this kit before the first lesson.

How is the refractive index of water calculated?

Measure the angle of incidence in air and the angle of refraction in water, then divide the sine of the first by the sine of the second. The result should be close to 1.33.

Why does the beam bend at the water surface?

Light travels more slowly in water than in air. When the beam crosses the surface at an angle, the change of speed changes its direction.

How should the tank be cleaned?

Empty it after each session, rinse with clean water, wipe with a soft cloth and let it dry. Avoid abrasive pads, which scratch the walls and scatter the beam.

Last Updated: September 2026