Waves and radiation

• When an object absorbs electromagnetic waves, it gains energy.
• X-rays have shorter wavelengths than visible light but longer than gamma rays.
• Electric fields are perpendicular to magnetic fields.
• Visible light has a range of wavelengths that are visible to the human eye.
• Radio waves have the longest wavelengths and lowest frequencies, while gamma rays have the shortest wavelengths and highest frequencies.
• The speed of light is constant, but the frequency changes.
• Wave speed = frequency x wavelength
• Frequency (f) is measured in Hertz (Hz). One hertz means one cycle per second.
• Electrons can absorb photons with enough energy to jump from one orbit to another.
• The amount of energy absorbed depends on the frequency of the wave.
• Infrared (IR) is used to heat objects or transmit signals without being detected by humans.
• The speed of light is constant regardless of its direction or source.
• Refraction happens when waves change direction as they pass into different materials.
• Reflection occurs when waves bounce off surfaces.
• All types of radiation comes from a radiation source like the sun, x-ray machines or a radioactive substance.
• We're always surrounded by radiation, either if it is radiation particles or radiation waves.
• Ionising radiation is a type of radiation has enough energy to removes tightly bound electrons from atoms, creating ions. This process can damage living tissues and genetic material.
• Non-ionising radiation has lower energy and is generally considered less harmful because it can't ionise atoms.
• Ionising radiation is a type of radiation that can cause mutations in DNA and cause cancer.
• Examples of ionising radiation is x-rays, gamma rays, cosmic rays and certain particles like alpha and beta particles.
• Examples of where non-ionising radiation is used: Microwave ovens, TV's and various electric devices.
• The human body absorbs some types of radiation more easily than others. For example, the skin absorbs UV light very well but X-rays are absorbed much deeper into our bodies.
• Gamma rays have no mass and no charge so they travel furthest through air and other materials. They are stopped by thick concrete walls.
• X-rays have no charge and are smaller than electrons. They can pass through most objects except lead.
• Ultraviolet (UV) light has a wavelength between visible light and X-rays. It is blocked out by glass or plastic windows.
• Radio waves have the longest wavelength of all EM waves. They can be reflected off metal surfaces.
• Infrared (IR) light has a longer wavelength than visible light. IR lamps are used to heat up food in microwaves.
• Periodic means that something repeats itself on a regular basis or with even spaces between them.
• Waves are oscillations that propagates.
• An oscillation is a periodic movement between two outer positions.
• The amplitude is the maximum displacement from equilibrium position.
• Frequency is the amount of oscillations per second and you can calculate it by dividing the amount of oscillations with the time it took for the wave to travel the distance.
• The unit Hertz (Hz) is the same as the unit 1/s.
• Waves consists of wave crests and troughs, which are the high and low points of the wave.
• The natural frequency is the frequency that an oscillation system gets when it oscillates freely in its natural state.
• The natural frequency of a diving board, is the frequency at which the board oscillates after you jump off it.
• Resonance happens when an oscillation system is in equilibrium with its natural frequency.
• When resonance occurs, the amplitude increases rapidly until something breaks or stops the oscillating motion.
• The direction a wave propagates os called the direction of travel to the wave.
• A longitudinal wave is a wave that happens in the oscillations along the direction of travel.