• Bending Light at PhET lets you change the frequency of the light, the angle of incidence, and the index of refraction of two media.

https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html

 

• Reflection and Refraction at oPhysics shows refraction, transmission, and reflection with continuously variable angle and indices of refraction in a more geometric and numerical presentation.

https://ophysics.com/l7.html

 

• Andrew Duffy at BU has created several refraction simulations. Refraction - Three Layers keeps the angle of incidence fixed while letting you observe refraction through three different media at once. 

https://physics.bu.edu/~duffy/HTML5/refraction_three_layer.html

•  While his Total Internal Reflection models an optical fibre.

https://physics.bu.edu/~duffy/HTML5/refraction_TIR.html