Total internal reflection/critical angle: Nakamura water tank.

Total internal reflection/critical angle: Nakamura water tank. Air Water Light Source Nakamura Refraction Tank 6V Battery The Nakamura Refraction Tank is a circular bath and light source. The tank is marked with degrees so that angles of incidence and reflection can be noted. The bath is filled halfway with water, and the light source swings and can be positioned anywhere along the rim of the tank. The beam of light is made visible by glancing along the white plastic back of the tank. Note: Use distilled water. Looking at figure 1A, a beam is sent from air into water. As the angle of incidence approaches 90 deg , as in figure 1B, the angle of refraction approaches a maximum, called the critical angle, which is 49 deg for the air/water system. If a beam is sent through the water towards the air at an angle greater than or equal to 49 deg , there will be total internal reflection, as shown in figure 1C. If the angle is less than 49 deg , then the beam will emerge from the water into the air, as shown in figure 1D. Ref: Modern College Physics by Harvey White, 6th ed., p.494-496