P1 Topic 2 - The Electromagnetic Spectrum Flashcards
How did Herschel discover infrared light in the 1800?
He used a prism to split up the sun’s white light to form the colour spectrum. Herschel then measured the temperature of each colour and found that red was the hottest while violet was the coldest. He then put a thermometer just past the colour red to find that it was even hotter. This was infrared light.
What are the seven EM waves in order of increasing frequency.
Radio waves Microwaves Infrared Visible Light Ultraviolet X-rays Gamma Rays
How did Ritter discover ultraviolet light in 1801?
Ritter knew that silver chloride became black when exposed to light so using a prism, he measured the time it took for strips to change to black in each colour. He discovered that colours nearer to the blue side had the fastest change and the area just beyond violet had the fastest change. Ritter had discovered ultraviolet light.
Name some of the dangers of microwaves.
Microwaves have a similar frequency to the vibrations of most molecules and therefore increase the vibrations of these molecules causing them to heat up. They can heat human body cells in this way.
Name some of the dangers of infrared.
Infrared frequencies can cause surface molecules to heat up. Infrared has more energy than microwaves so can cause more damage in less time. It can cause skin burns.
Name some of the dangers of ultraviolet.
UV has more energy and a higher frequency than IR making it ionising, so it carries enough energy to knock off electrons from atoms. Sunburn happens when skin cells become damaged from the UV light from the sun. This can cause cell mutation which leads to skin cancer. UV light can also cause eye damage.
Name some of the dangers of gamma and X-rays.
These are very high frequency waves. They carry more energy than the other EM waves and can penetrate further into the body causing more damage. This can lead to cell mutation and cancer.
What are radio waves used for?
Communication:
Long wave radio waves bend around the curvature of the Earth and are used for long range communication (half way around the world)
Short to medium wave radio is transmitted so that it bounces off the ionosphere in the atmosphere.
TV and FM radio waves have to in the line of sight of the receiver as they can’t travel around hills or buildings etc.
Very short radio waves can pass through the atmosphere to communicate with satellites.
What are microwaves used for?
Communication:
Communication to and from satellites uses microwaves as they can pass through the watery atmosphere.
Microwaves:
Microwaves are absorbed by water molecules in food, causing the water to heat up. The rest of the food then warms up through convection or conduction.
What are infrared waves used for?
Monitoring temperature:
IR is given off by hot objects and the hotter the object, the more IR it gives off. Therefore, IR sensors can be used as cameras to detect heat.
Optical fibres:
Optical fibres can be used to transmit IR signals over long distances. The IR bounces of the surface of the optical fibre until it reaches its destination.
Other:
TV remotes, toasters, IR security systems
What is visible light used for?
…
Seeing…
What is ultraviolet light used for?
It can be used to detect forged bank notes.
Disinfecting water.
What are X-rays used for?
Radiography - X-rays
Airport security
What are gamma rays used for?
Radiotherapy - Gamma rays kill all living cells and can be used to kill cancer.
Sterilisation of food or surgical equipment
