# Questions on light refraction

1. Sep 7, 2011

### Misr

1-when a light ray falls on a piece of glass,it refracts. which of the following concepts doesn't change : speed-frequency-wavelength
indeed speed does change because of changing the medium but frequency doesn't .
what causes wave length to change?change in speed?(V=freq*wavelength)
right?do u have a better explanation?

2-when light falls from a medium of lower optical density to that of higher optical density with an angle of incidence=zero ,of course direction doesn't change but what about speed??speed changes as a result of changing the medium.right?

2. Sep 7, 2011

hello there?

3. Sep 7, 2011

### Staff: Mentor

Hi. Sorry, not all threads are quickly responded to. I don't know the answers to your questions myself, and the people that do might not be online. Just be patient.

4. Sep 8, 2011

### Claude Bile

When a wave moves from one medium into another with different refractive index, it is the velocity and wavelength that change, while the frequency remains constant.

The frequency must be invariant to satisfy the condition that the fields are continuous across the boundary at all times.

Claude.

5. Sep 8, 2011

### LJW

Claude is correct. Frequency will always remain constant, as frequency is source dependent. Velocity changes as it moves into a medium with a different refractive index, which then changes the wavelength. Obviously, if v increases λ increases proportionally and vice versa.