Radio waves have the smallest frequency and longest wavelength. This is why they are not dangerous. Microwaves have the next longest wavelength and are what are used to warm up cold foods. Infrared waves are the next longest wavelength and border the red light on the visible spectrum. Infrared waves are used in remote controls and night vision. Visible light is next and is what we can see with our eyes. Next is ultraviolet, which borders the violet light on the visible spectrum. These are the damaging rays by the sun and are essentially “super-violet” rays. Next is X-rays. These have very high frequencies and are dangerous in high quantities. Gamma rays are the shortest wavelength and the highest frequency and the most dangerous. These cosmic rays often come from stars and other celestial objects.

When waves interfere with one another, they pass through each, and others can undergo either constructive or destructive interference.  In constructive interference, waves add together to produce a briefly more massive wave.  In destructive interference, waves subtract from each other to create a smaller wave.  However, once the waves move past one another, they will return to their original shape and size.

Waves carry energy along the path displacing the matter for a brief period. However, the matter does not travel along the wave and instead will return to its natural rest position once the wave moves past it. For example, an ocean wave can travel many miles without displacing the entire ocean.

Transverse waves are waves whose particles travel perpendicular to the direction that the wave itself is traveling. Electromagnetic waves are another example of transverse waves.

The relationship between wavelength and frequency is given by the equation  where  is the wavelength,  is the speed of light, and  is frequency.

We are given the values for frequency and the speed of light, allowing us to solve for the wavelength.

Electromagnetic waves all travel at the same speed which is the speed of light.  The speed of light in a vacuum is nearly 

Electromagnetic waves are the only type of wave that does not require a medium to travel. Light, radio, and microwaves are examples of electromagnetic waves. Sound does require a medium to travel. In a vacuum, soundwaves cannot travel as there is no air to compress.

Longitudinal waves are waves whose particles travel parallel to the direction that the wave itself is traveling. Sound waves are another example of longitudinal waves.

The speed of the wave along the Slinky depends on the mass of the Slinky itself and the tension caused by stretching it. Since both of these things have not changed, the wave speed remains constant.

The wave speed is equal to the wavelength multiplied by the frequency.

Since she is moving her hand faster, the frequency has increased. Since the velocity has not changed, an increase in the frequency would decrease the wavelength.

Sound is often described in terms of the vibration of the molecules of the medium in which it travels (in other words, the displacement of the molecules). Sound can also be viewed from a pressure point of view because this variation in pressure is easier to measure. In compression, the pressure is higher because the molecules are closer together. In rarefaction, there is an expansion of molecules and, therefore, a lower pressure.