A ray of light passes at an angle from air into glass and bends. Which property of the light is unchanged?

1. Refraction happens at the boundary between two media when the speed of light changes. 2. The speed of the light changes, but the frequency of the light remains the same. 3. Because the ray strikes the boundary at an angle, its direction also changes. 4. That change of direction is what makes a straw in a glass of water look bent. _Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 5: Geometrical optics_