In the given scenario, light waves are incident on an air-glass boundary, and some of the light waves are reflected while others are refracted. The question asks which property is the same for the incident wave and the refracted wave.

Option 1: Speed. Speed refers to how quickly the light wave is traveling. When light waves travel from one medium to another, such as from air to glass, their speed changes. Therefore, the speed is not the same for the incident and refracted waves.

Option 2: Direction. Direction refers to the path that the light wave is following. When light waves encounter a boundary between two mediums, such as air and glass, their direction changes. This change in direction is known as refraction. Therefore, the direction is not the same for the incident and refracted waves.

Option 3: Brightness. Brightness refers to the intensity or level of light. When light waves encounter a boundary and are reflected or refracted, their brightness can change. Therefore, the brightness is not the same for the incident and refracted waves.

Option 4: Frequency. Frequency refers to the number of wave cycles per second and determines the color of light. Frequency remains constant when light waves travel from one medium to