P1.2 The Electromagnetic Spectrum Flashcards
What are the seven types of EM waves in order of decreasing wavelength?
Radio Waves, micro waves, infrared, visible light, ultraviolet, x-rays, gamma rays.
Are EM waves longitudinal or transverse waves?
Transverse waves.
What is the order of visible light colours starting at Red?
Red Orange Yellow Green Blue Indigo Violet
How and who by was Infrared discovered?
Herschel discovered IR when he measured all the temperatures of refracted light when he noticed that the hottest was just beyond red. He had discovered invisible IR waves.
How and who by was ultraviolet discovered?
Ritter knew that silver chloride turned from white to black when exposed to light. He wanted to see which colour made it change quickest. He refracted light and placed silver chloride coated chips under each colour and one just beyond violet, where it turned black quickest of all.
Which EM waves tend to be absorbed and which tend to be able to pass through material?
The EM waves nearer the end of the spectrum tend to be able to pass through things whilst those in the middle tend to be absorbed.
How does wave frequency effect the energy?
The higher the frequency, the more energy they have and so the more harmful the radiation.
How can microwaves be harmful?
They have a similar frequency to vibrations so they increase them, resulting in microwaves being able to heat human body cells. There have been suggested links between mobile phones and brain tumours, but nothing has been proven.
How can IR waves be harmful?
They have the same heating effect as microwaves, but with much mow energy, so it causes more heating. It can cause skin burns, if there is too much exposure.
How can UV waves be harmful?
It is ionising, meaning it has enough energy to knock electrons off atoms. Sunburn is caused by skin cells absorbing too many UV rays. UV can cause cell mutations which can lead to cancer. For UV it is particularly skin cancer.
How can x-rays or gamma rays be harmful?
They have much more energy and can penetrate much further into the body and be much more damaging. They can cause cell mutations and cancer with a higher risk.
What are some of the uses of Radio waves?
Communication
TV signals
Radio signals
Communication with satellites
What are the advantages of using radio waves with long wavelengths?
They can go through hills and tunnels.
Why are very short wave radio waves used for satellite communications?
They can pass through the ionosphere.
How does a microwave use micro waves to heat up your food?
The energy from the microwaves is absorbed by the water molecules in the food and the energy is conducted to other parts of the food, which heats it up.
How is IR used in crime detection?
Night vision cameras and equipment use IR to detect hotter things such as a criminal in a hiding place of colder places like bushes or trees.
What uses does IR have inside the home?
Cooking eg toasters
Remote controls for the TV
Transmit information between computers and mobiles
In security systems eg burglar alarms.
How is UV used in detecting forgeries?
Bank notes have special fluorescent markings that only show under UV. If the police use UV they can see the markings if it is genuine.
How are x-rays used in hospital?
They produce x-ray pictures. The waves can easily pass through flesh but less bones, so it creates an image of the bones. They are used to check if any bones are broken.
How are gamma rays used in treating cancer?
High doses of gamma rays kill all cells. So if they are directed at the cancer, they can kill the cancer cells. This is called radiotherapy.
How are gamma rays used is sterilisation?
Gamma rays are used to treat food and surgical instruments as it will kill off any microbes that may be on the equipment.
What are the other types of ionising radiation apart from gamma rays?
Alpha and beta.
