Physics
Snell's law is

Is the line that is perpendicular to the separation of the 2 media.
Speed of light is the
We see objects because ...
Electromagnetic Spectrum is ...
Optical fibres are ...
Longitudinal waves ...
Difference of Frequency and Hertz (frequency unit) is
Refraction of any wave is ...
Sound waves are caused by vibrations, are longitudinal waves, need a material to travel through, can be diffracted, etc. These are some of the ...
Scanning the womb of a pregnant woman is one of the applications of:
Photons are ...
If we say that an Electromagnetic wave has high frequency means ...

According to this picture:

This picture is an example of: