Option 1 states that the frequency of a light wave remains unchanged when it travels from air to glass. This statement is incorrect. When a light wave travels from one medium to another, such as from air to glass, its frequency does not stay the same. In fact, the frequency of the light wave remains constant throughout its journey. Therefore, option 1 is false.

Option 2 states that the speed of a light wave changes when it travels from air to glass. This statement is true. The speed of light changes depending on the medium it travels through. In this case, when light travels from air to glass, its speed decreases. This change in speed is due to the difference in refractive indexes between air and glass. Therefore, option 2 is correct.

Given that option 1 is false and option 2 is true, the correct answer is option 3 - Both 1 and 2. So, when light waves travel from air to glass, their frequency remains constant, but their speed decreases.