P13: EM Waves Flashcards
What are the electromagnetic waves in order of decreasing wavelength?
Radio, Microwaves, Infrared, Visible Light, UV Radiation, X rays, Gamma Rays
Decreasing wavelength, increasing frequency/energy.
What is the speed of EM waves?
All EM waves travel at the speed of 3x10^8 m/s through space or in a vacuum.
Describe method to investigate the radiation/absorption of different materials.
- Align infrared detector with one side of a Leslie Cube, 20cm away and take the initial temperature.
- Heat one side of the Leslie Cube by pouring hot water onto the surface.
- Measure and record temperature of surface every 30s.
- Repeat for different surface, usually matt black, shiny, white.
- Record results for each surface. Greater temperature = Emits more radiation.
How is infrared radiation used?
- Infrared radiation is absorbed by skin and heats up cells.
- Optical fibres in communication systems usually use infrared radiation as its absorbed less by glass fibres. Used for remote controls to transmit signals.
- Infrared radiation can be used for cooking food/infrared cameras as it transfers thermal energy.
What are microwaves used for?
- Microwaves are used for communications, e.g. satellite TV because they can pass through atmosphere. Also carry phone signals.
- Used for cooking food as they penetrate food and are absorbed by water molecules.
What are radio waves used for?
- Long wavelength means they can travel far without losing quality.
- Used go carry radio, TV and mobile phone signals. Can penetrate people’s bodies and heat internal parts.
- Long wavelength used in international radio stations as they have longer range. TV broadcasting uses low wavelength as they carry more information.
What are carrier waves?
They are waves that carry any type of signal e.g. microwaves, radio waves, depending on the amount of information or distance.
What does it mean if waves are shorter wavelength?
It means more information can be carried, shorter range due to decreased absorption by atmosphere, spread out less.
What are microwaves used for?
- They are used for satellite and TV links as they spread out less so signal doesn’t weaken.
What are optical fibres?
They are used to transmit signals by light and infrared radiation. Carry much more information and are more secure.
What are the characteristics of ultraviolet?
- They radiate the least heat but most energy.
- Harmful to human eyes due to high amounts of energy. Harmful to skin.
What are the similarities and differences of x rays and gamma rays?
Similarities: They both travel straight into substances and can pass through them if they are not too thick or dense. Short wavelength, carry more energy. Both used in medical imagining and treatment. Both are ionising radiation which can damage/kill cells and cause cancer.
Differences: Gamma rays are produced by radioactive substances. Gamma rays have shorter wavelength so penetrate substances more. Gamma rays can be used to destroy cancer tumours by aiming beam at it without harming surrounding tissue (radiation therapy).
