What are they?
- They are transverse waves that transfer energy from the source of the waves to an absorber
- Basically they carry energy to transport it to the receiving medium
- Example: Light is an electromagnetic wave, where in the light originates from the sun (source) and is transported to the earth(absorber)
Properties of Electromagnetic Waves
- Transverse waves
- Can travel through a vacuum (Do not require a medium for propagation)
- There are 7 types of EM waves:
- Radio waves
- Microwaves
- Infrared
- All hot objects emit infrared radiation
- The emitted waves can then be absorbed by other objects, warming them up
- Visible light (red, orange, yellow, green, blue, indigo, violet)
- Ultraviolet
- X rays
- Gamma rays
- As the energy carried by the EM wave increases, the more dangerous it becomes
- The higher the frequency, the higher the energy of the radiation
- Radiation with higher energy is:
- Harmful to cells and tissues causing cancer (e.g. UV, X-rays, Gamma rays) [Wear sunscreen!]
- Radiation with lower energy is:
- Useful for communications
- Less harmful to humans
Energy Transfers from the Sun
- The Sun emits several types of EM radiation, including:
- Visible light waves allow living creatures to see
- Infrared waves heat up the Earth
- Ultraviolet waves provide plants with the energy for photosynthesis which they need to grow
Additional note:
- Wavelength and frequency are inversely proportional
- All electromagnetic waves travel at the same speed in a vacuum ($3$ x $10^8$ m/s)
Properties of visible light
- Different wavelengths can slow down by different amounts – an effect known as dispersion (not just for visible light but for any kinda wave)
- This effect is seen clearly with visible light and is responsible for the separation of white light into its constituent colours when it passes through a prism
- This is done by refraction
- Violet light is refracted the most, whilst red light is refracted the least
- This splits up the colours to form a spectrum