- The principle of reflection functions through angles to the normal, an imaginary line drawn perpendicular to a surface. When a wave strikes a surface, it will reflect back at an angle to the normal equal to the angle to the normal at which it strikes (these are called the angle of reflection and the angle of incidence, respectively). By placing a barrier, such as a metal bar, in the ripple tank, the produced waves will reflect off of the bar accordingly.
- Refraction is the instance in which waves change direction due to a change in speed. In water, waves travel faster in deeper water. Placing a sheet of water in the ripple tank will alter the depth of the water at certain spots. The produced waves, when traveling from the deeper part to the shallower part, will refract. Depending on the change in depth, the waves will either bend toward or away from the normal of the sheet of glass.
- Diffraction is the result of waves hitting obstacles. For example, when a traveling wave hits an obstacle, the wave will bend around the obstacle after hitting it. The effects are more prominent when the size of the obstacle is comparable to that of the wavelength. In a ripple tank, placing an obstacle with a small gap (e.g. two walls with a hole in between) will produce diffraction. The waves will crowd through the opening and then spread outward, creating an arc effect.
- Interference is the result of two or more waves colliding. Waves oscillate between crests and troughs --- mathematically speaking, a wave can have positive or negative values. When two waves meet, they "add" together. If a wave with a negative value meets a wave of positive value, they cancel out. This is called destructive interference. If two oscillating paddles are placed in a ripple tank, the produced waves will crash into each other and add together or cancel each other out. This will produce an interference pattern composed of areas of activity and areas of nothing.
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